feat: Make the H.264 profile-level-id configurable.

[th-aslam]

As discussed in H.264 fmtp in jicofo offers (42e01f) — deliberate interop floor or 2017 legacy? with @jallamsetty1: jicofo hardcodes 42e01f (Constrained Baseline) in every H.264 offer, a value dating to the 2017 Firefox workaround (#308). Some platform encoder factories don't advertise CBP while libwebrtc matches profiles exactly, so senders on those platforms silently fall back to software encoding — macOS VideoToolbox advertises only Baseline/Main/High (offering 42001f on the same machine flips it to hardware encode, powerEfficient: true), and MediaFoundation on Windows reportedly behaves the same.

This makes the value configurable:

• New config: jicofo.codec.video.h264.profile-level-id, default "42e01f" — the offer output is byte-identical to current behavior at default config (the existing param cramming is deliberately untouched to keep the change minimal).
• H264CodecConfig follows the existing RtxCodecConfigWithLegacy pattern, preserving the legacy ENABLE_H264/H264_PT properties.
• Tests: default asserts the exact current fmtp string; withNewConfig covers an overridden value.

A companion lib-jitsi-meet PR making the client-side H.264 profile filtering in TPCUtils.ts configurable will follow, per the same thread.

[jitsi-jenkins]

Hi, thanks for your contribution!
If you haven't already done so, could you please make sure you sign our CLA (https://jitsi.org/icla for individuals and https://jitsi.org/ccla for corporations)? We would unfortunately be unable to merge your patch unless we have that piece :(.