Replace default database icons

[wolframroesler]

Replace database icons (aka default icons) by SVG files from the Icons8 collection (https://icons8.com/). Show icons larger than 16x16 because the SVGs allow it and it looks awesome. Also cleaned up the icon loading C++ functions a bit (added size parameter where needed, eliminated unused functions, etc.)

Some icons aren't freely available in SVG format yet, using PNG for those. Will replace ASAP.

Feel free to squash the commits, however I'd keep the C++ and icon changes separate.

NOTE: Someone must make sure that Icon8 is properly credited.

Fixes #4071.

Screenshots

Testing strategy

Tested manually. Updated unit tests where appropriate.

Type of change

• ✅ New feature (change that adds functionality)

[wolframroesler]

I rebased develop into the branch to get rid of a few conflicts, and now some unit tests are failing. Works on develop and on HEAD^. Can you have a look, @droidmonkey?

$ make test
Running tests...
Test project /home/wolfram/src/keepassxc/build
      Start  1: testgroup
 1/39 Test  #1: testgroup ........................***Exception: Child aborted  0.15 sec
      Start  2: testkdbx2
 2/39 Test  #2: testkdbx2 ........................   Passed    0.07 sec
      Start  3: testkdbx3
 3/39 Test  #3: testkdbx3 ........................***Exception: Child aborted  0.15 sec
      Start  4: testkdbx4
 4/39 Test  #4: testkdbx4 ........................***Exception: Child aborted  0.15 sec
      Start  5: testkeys
 5/39 Test  #5: testkeys .........................   Passed    0.81 sec
      Start  6: testgroupmodel
 6/39 Test  #6: testgroupmodel ...................   Passed    0.07 sec
      Start  7: testentrymodel
 7/39 Test  #7: testentrymodel ...................   Passed    0.07 sec
      Start  8: testcryptohash
 8/39 Test  #8: testcryptohash ...................   Passed    0.06 sec
      Start  9: testsymmetriccipher
 9/39 Test  #9: testsymmetriccipher ..............   Passed    0.09 sec
      Start 10: testsignature
10/39 Test #10: testsignature ....................   Passed    0.29 sec
      Start 11: testhashedblockstream
11/39 Test #11: testhashedblockstream ............   Passed    0.06 sec
      Start 12: testkeepass2randomstream
12/39 Test #12: testkeepass2randomstream .........   Passed    0.06 sec
      Start 13: testmodified
13/39 Test #13: testmodified .....................   Passed    9.80 sec
      Start 14: testdeletedobjects
14/39 Test #14: testdeletedobjects ...............***Exception: Child aborted  0.15 sec
      Start 15: testkeepass1reader
15/39 Test #15: testkeepass1reader ...............***Exception: Child aborted  0.14 sec
      Start 16: testopvaultreader
16/39 Test #16: testopvaultreader ................   Passed    0.58 sec
      Start 17: testwildcardmatcher
17/39 Test #17: testwildcardmatcher ..............   Passed    0.01 sec
      Start 18: testupdatecheck
18/39 Test #18: testupdatecheck ..................   Passed    0.06 sec
      Start 19: testautotype
19/39 Test #19: testautotype .....................   Passed    7.88 sec
      Start 20: testopensshkey
20/39 Test #20: testopensshkey ...................   Passed    1.12 sec
      Start 21: testsshagent
21/39 Test #21: testsshagent .....................   Passed    1.80 sec
      Start 22: testentry
22/39 Test #22: testentry ........................   Passed    0.07 sec
      Start 23: testmerge
23/39 Test #23: testmerge ........................   Passed    0.29 sec
      Start 24: testpasswordgenerator
24/39 Test #24: testpasswordgenerator ............   Passed    0.68 sec
      Start 25: testpasswordhealth
25/39 Test #25: testpasswordhealth ...............   Passed    0.02 sec
      Start 26: testpassphrasegenerator
26/39 Test #26: testpassphrasegenerator ..........   Passed    0.07 sec
      Start 27: testhibp
27/39 Test #27: testhibp .........................   Passed    0.06 sec
      Start 28: testtotp
28/39 Test #28: testtotp .........................   Passed    0.07 sec
      Start 29: testbase32
29/39 Test #29: testbase32 .......................   Passed    0.01 sec
      Start 30: testcsvparser
30/39 Test #30: testcsvparser ....................   Passed    0.01 sec
      Start 31: testrandomgenerator
31/39 Test #31: testrandomgenerator ..............   Passed    0.01 sec
      Start 32: testentrysearcher
32/39 Test #32: testentrysearcher ................   Passed    0.02 sec
      Start 33: testcsvexporter
33/39 Test #33: testcsvexporter ..................   Passed    0.06 sec
      Start 34: testykchallengeresponsekey
34/39 Test #34: testykchallengeresponsekey .......   Passed    0.08 sec
      Start 35: testsharing
35/39 Test #35: testsharing ......................   Passed    0.54 sec
      Start 36: testdatabase
36/39 Test #36: testdatabase .....................   Passed    0.45 sec
      Start 37: testtools
37/39 Test #37: testtools ........................   Passed    0.01 sec
      Start 38: testfdosecrets
38/39 Test #38: testfdosecrets ...................   Passed    0.07 sec
      Start 39: testbrowser
39/39 Test #39: testbrowser ......................   Passed    0.09 sec

87% tests passed, 5 tests failed out of 39

Total Test time (real) =  26.19 sec

The following tests FAILED:
	  1 - testgroup (Child aborted)
	  3 - testkdbx3 (Child aborted)
	  4 - testkdbx4 (Child aborted)
	 14 - testdeletedobjects (Child aborted)
	 15 - testkeepass1reader (Child aborted)
Errors while running CTest
Makefile:85: recipe for target 'test' failed
make: *** [test] Error 8

[wolframroesler]

Resolved the conflicts. Unit tests still fail.

[droidmonkey]

I still have this in my queue. I want to replace some icons

[droidmonkey]

Updated all icons to either be licensed MIT, CC0, or my original work. Some icons are derivative works of MIT/CC0 icons. Those are clearly annotated in the makedbicons.sh script file.

Also took this opportunity to complete the application icons:

[droidmonkey]

@phoerious completed svg minify, this PR is ready to go.

[phoerious]

One small remark, rest looks good.