Refactor message encryption and pairing code

[pan-apple]

Problem

The packet encryption/decryption code is duplicated in SecureSessionMgr and RendezvousSession classes. The code can use some refactoring.

Summary of Changes

• Extract message encryption/decryption to its own functions.
  These can be reused for pairing, and CASE based session setup.
• Cleanup pairing and rendezvous code to use the new functions.
• Use SecureSessionMgr to send encrypted messages generated by Rendezvous process.

[github-actions]

Size increase report for "esp32-example-build" from 6243e6a

File	Section	File	VM
chip-all-clusters-app.elf	.flash.rodata	-376	-376
chip-all-clusters-app.elf	.flash.text	-508	-508

Full report output

BLOAT REPORT

Files found only in the build output:
    report.csv

Comparing ./master_artifact/chip-all-clusters-app.elf and ./pull_artifact/chip-all-clusters-app.elf:

sections,vmsize,filesize
.debug_info,0,25100
.debug_line,0,3068
.debug_abbrev,0,2637
.debug_str,0,440
[Unmapped],0,376
.debug_ranges,0,208
.strtab,0,84
.xt.prop._ZN4chip9Transport19PeerConnectionStateaSEOS1_,0,80
.debug_aranges,0,16
.debug_frame,0,-8
.symtab,0,-32
.xt.lit._ZNK4chip8OptionalINS_9Transport11PeerAddressEE5ValueEv,0,-40
.xt.prop._ZN4chip9Transport15PeerConnectionsILj16ELNS_4Time6SourceE0EE23FindPeerConnectionStateENS_8OptionalIyEEtPNS0_19PeerConnectionStateE,0,-40
.xt.prop._ZNK4chip20RendezvousParameters12IsControllerEv,0,-40
.shstrtab,0,-76
.xt.prop._ZN4chip8OptionalIyEaSERKS1_,0,-76
.debug_loc,0,-341
.flash.rodata,-376,-376
.flash.text,-508,-508

[github-actions]

Size increase report for "nrfconnect-example-build" from 6243e6a

File	Section	File	VM
chip-lighting.elf	rodata	-352	-352
chip-lighting.elf	text	-384	-384
chip-lock.elf	rodata	-352	-352
chip-lock.elf	text	-384	-384

Full report output

BLOAT REPORT

Files found only in the build output:
    report.csv

Comparing ./master_artifact/chip-shell.elf and ./pull_artifact/chip-shell.elf:

sections,vmsize,filesize

Comparing ./master_artifact/chip-lighting.elf and ./pull_artifact/chip-lighting.elf:

sections,vmsize,filesize
.debug_info,0,25758
.debug_line,0,2884
.debug_abbrev,0,2562
.debug_str,0,456
.strtab,0,134
.debug_ranges,0,96
.debug_aranges,0,16
.symtab,0,16
.shstrtab,0,-2
.debug_loc,0,-92
rodata,-352,-352
text,-384,-384

Comparing ./master_artifact/chip-lock.elf and ./pull_artifact/chip-lock.elf:

sections,vmsize,filesize
.debug_info,0,25758
.debug_line,0,2884
.debug_abbrev,0,2562
.debug_str,0,456
.strtab,0,134
.debug_ranges,0,96
.debug_aranges,0,16
.symtab,0,16
.shstrtab,0,-2
.debug_loc,0,-92
rodata,-352,-352
text,-384,-384

[pan-apple]

@saurabhst, @jelderton, @BroderickCarlin, any feedback?

[jelderton]

Sorry, I may have merged too soon. I just saw that you asked for a couple more people to take a look.

[pan-apple]

Sorry, I may have merged too soon. I just saw that you asked for a couple more people to take a look.

@jelderton, that's totally fine. Only one of the requested reviews was needed.