[example/nrfconnect] Added support for sending UDP broadcast messages.

[kkasperczyk-no]

Problem

nrfconnect platform doesn't support sending UDP broadcast messages
periodically by PublishService as other platforms do (e.g. nrf5)

Summary of Changes

• Added Service component with PublishService implementation
  to support sending UDP broadcast messages.

Fixes #3088

[github-actions]

Size increase report for "nrfconnect-example-build"

File	Section	File	VM
chip-lighting.elf	text	316	316
chip-lighting.elf	rodata	36	36
chip-lighting.elf	bss	0	16
chip-lighting.elf	[LOAD #1 [RWX]]	4	4
chip-lighting.elf	[LOAD #3 [RW]]	0	-16
chip-lock.elf	text	316	316
chip-lock.elf	rodata	40	40
chip-lock.elf	[LOAD #3 [RW]]	0	16
chip-lock.elf	bss	0	16
chip-lock.elf	[LOAD #1 [RWX]]	4	4

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,0,34877
.debug_line,0,4420
.debug_abbrev,0,2788
text,316,316
.debug_loc,0,315
.debug_str,0,313
.strtab,0,230
.symtab,0,176
.debug_ranges,0,120
.debug_frame,0,60
rodata,36,36
.debug_aranges,0,32
bss,16,0
[LOAD #1 [RWX]],4,4
[Unmapped],0,-7
[LOAD #3 [RW]],-16,0

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

sections,vmsize,filesize
.debug_info,0,34873
.debug_line,0,4410
.debug_abbrev,0,2788
.debug_loc,0,319
text,316,316
.debug_str,0,313
.strtab,0,230
.symtab,0,176
.debug_ranges,0,120
.debug_frame,0,60
rodata,40,40
.debug_aranges,0,32
[LOAD #3 [RW]],16,0
bss,16,0
[LOAD #1 [RWX]],4,4
[Unmapped],0,-5