Disallow VLAs in Matter code

[bzbarsky-apple]

Problem

VLAs can be dangerous, especially when sized based on network inputs.

Change overview

Stop using VLAs in most places, whitelist a few places that are tracked by open issues, and add -Wvla so no more places will get added accidentally.

Testing

Compiles and passes CI. No behavior changes.

[todo]

This VLA is not OK. See #8558 }}

connectedhomeip/src/app/zap-templates/templates/app/CHIPClientCallbacks-src.zapt

Lines 356 to 363 in fd767da

	{{! TODO: This VLA is not OK. See https://github.com/project-chip/connectedhomeip/issues/8558 }}
	#pragma GCC diagnostic push
	#pragma GCC diagnostic ignored "-Wvla"
	{{chipType}} data[count];
	#pragma GCC diagnostic pop
	for (size_t i = 0; i < count; i++)
	{
	{{#if isStruct}}

---

This comment was generated by todo based on a TODO comment in fd767da in #9476. cc @bzbarsky-apple.

[github-actions]

Size increase report for "esp32-example-build" from 1e5a48b

File	Section	File	VM
chip-temperature-measurement-app.elf	.flash.text	-36	-36
chip-ipv6only-app.elf	.flash.text	-172	-172

Full report output

BLOAT REPORT

Files found only in the build output:
    report.csv

Comparing ./master_artifact/chip-pigweed-app.elf and ./pull_artifact/chip-pigweed-app.elf:

sections,vmsize,filesize

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

sections,vmsize,filesize

Comparing ./master_artifact/chip-bridge-app.elf and ./pull_artifact/chip-bridge-app.elf:

sections,vmsize,filesize

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

sections,vmsize,filesize

Comparing ./master_artifact/chip-temperature-measurement-app.elf and ./pull_artifact/chip-temperature-measurement-app.elf:

sections,vmsize,filesize
[Unmapped],0,36
.flash.text,-36,-36

Comparing ./master_artifact/chip-persistent-storage.elf and ./pull_artifact/chip-persistent-storage.elf:

sections,vmsize,filesize

Comparing ./master_artifact/chip-ipv6only-app.elf and ./pull_artifact/chip-ipv6only-app.elf:

sections,vmsize,filesize
.flash.text,-172,-172
[Unmapped],0,-3924

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

sections,vmsize,filesize