[FEATURE]: Add observability metrics for media decoding and HTTP downloads

[rmccorm4]

Add observability metrics for things related to multimodality, media decoding, media URL downloads. Some examples:

• Performance of decoding, HTTP
• Memory usage
• Sizes, types, codecs, etc, stats

Related PRs:

• feat: Media processing in the frontend - 1st pass #3630
• feat: Media HTTP fetching and b64 decoding #3967
• feat: Image decoder in the frontend #3971
• feat: decoded media via NIXL #3988