docs(core): Polish API docs for Metadata

[Xuanwo]

Which issue does this PR close?

None

Rationale for this change

None

What changes are included in this PR?

Polish API docs for Metadata

Are there any user-facing changes?

API Docs

[codspeed-hq]

CodSpeed Performance Report

Merging #5497 will degrade performances by 15.89%

_{Comparing polish-api (df43c3f) with main (8549524)}

Summary

⚡ 8 improvements
❌ 4 regressions
✅ 61 untouched benchmarks

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Benchmarks breakdown

	Benchmark	main	polish-api	Change
❌	buffer 256 KiB * 32 chunk	154.4 ns	183.6 ns	-15.89%
❌	buffer 256 KiB * 4 chunk	154.4 ns	183.6 ns	-15.89%
❌	buffer 4.00 MiB * 32 chunk	154.4 ns	183.6 ns	-15.89%
❌	buffer 4.00 MiB * 4 chunk	154.4 ns	183.6 ns	-15.89%
⚡	256 KiB * 1000k chunk	183.6 ns	154.4 ns	+18.88%
⚡	256 KiB * 1000k truncate	245.8 ns	216.7 ns	+13.46%
⚡	256 KiB * 100k chunk	183.6 ns	154.4 ns	+18.88%
⚡	256 KiB * 100k truncate	245.8 ns	216.7 ns	+13.46%
⚡	256 KiB * 10k chunk	183.6 ns	154.4 ns	+18.88%
⚡	256 KiB * 10k truncate	245.8 ns	216.7 ns	+13.46%
⚡	256 KiB * 1k chunk	212.8 ns	183.6 ns	+15.89%
⚡	256 KiB * 1k truncate	245.8 ns	216.7 ns	+13.46%