[platform] remove legacy functions in ConnectivityManager

[gjc13]

Problem

• Function HaveIPv4InternetConnectivity and HaveIPv6InternetConnectivity are not used.
• Service connectivity is a legacy concept and not well defined.

Change overview

Remove these functions from ConnectivityManager.

Testing

How was this tested? (at least one bullet point required)

• CI build & run

[github-actions]

Size increase report for "gn_qpg-example-build" from 45715cc

File	Section	File	VM
chip-qpg6100-lighting-example.out	.text	-32	-32

Full report output

BLOAT REPORT

Files found only in the build output:
    report.csv

Comparing ./master_artifact/chip-qpg6100-lighting-example.out and ./pull_artifact/chip-qpg6100-lighting-example.out:

sections,vmsize,filesize
[Unmapped],0,32
.debug_loc,0,27
.shstrtab,0,-2
.debug_abbrev,0,-25
.strtab,0,-30
.symtab,0,-32
.text,-32,-32
.debug_line,0,-115
.debug_ranges,0,-200
.debug_str,0,-1217
.debug_info,0,-3986

Comparing ./master_artifact/chip-qpg6100-lighting-example.out.map and ./pull_artifact/chip-qpg6100-lighting-example.out.map:

BLOAT EXECUTION FAILED WITH CODE 1:
bloaty: unknown file type for file './pull_artifact/chip-qpg6100-lighting-example.out.map'

[github-actions]

Size increase report for "nrfconnect-example-build" from 45715cc

File	Section	File	VM
chip-lock.elf	text	-32	-32

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
.debug_loc,0,56
.debug_line,0,3
.debug_str,0,-1052
.debug_info,0,-2031

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

sections,vmsize,filesize
.debug_loc,0,22
.shstrtab,0,2
.debug_frame,0,-4
.strtab,0,-30
.symtab,0,-32
text,-32,-32
.debug_line,0,-121
.debug_ranges,0,-176
.debug_str,0,-1218
.debug_info,0,-4111

[gjc13]

@bzbarsky-apple @andy31415 PTAL