Mdns broke running the server examples locally on macOS

[vivien-apple]

Problem

#4132 is cool. But in the current state it broke my current setup on macOS. It builds fine but the server is not running well as err = Mdns::ServiceAdvertiser::Instance().Start returns an error there.

Summary of Changes

• Add #if CHIP_ENABLE_MDNS in examples/common/chip-app-server/Server.cpp

[andy31415]

Marked as hotfix: simple change and fixes developer brokedness.

[andy31415]

We probably will want something that integrates with iOS mdns framework (will need similar with linux as well), so that we can run examples locally and still benefit from discovery.

[github-actions]

Size increase report for "nrfconnect-example-build" from fb65a31

File	Section	File	VM
chip-lighting.elf	shell_root_cmds_sections	-8	-8
chip-lighting.elf	text	-88	-88
chip-lock.elf	shell_root_cmds_sections	-8	-8
chip-lock.elf	text	-88	-88

Full report output

BLOAT REPORT

Files found only in the build output:
    report.csv

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

sections,vmsize,filesize
shell_root_cmds_sections,-8,-8
.debug_abbrev,0,-63
text,-88,-88
.debug_str,0,-118
.debug_ranges,0,-128
.debug_line,0,-255
.debug_loc,0,-314
.debug_info,0,-1042

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

sections,vmsize,filesize
shell_root_cmds_sections,-8,-8
.debug_abbrev,0,-63
text,-88,-88
.debug_str,0,-118
.debug_ranges,0,-128
.debug_line,0,-251
.debug_loc,0,-310
.debug_info,0,-1042

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

sections,vmsize,filesize