[Review] test(boxsdkgen): Update Metadata Taxonomies tests (box/box-codegen#909)

[govambam]

Recreated from box#1282 for Macroscope review.

Original PR: box#1282
Status: closed (merged)

Recreated using squash merge commit - exact merged state preserved.

Original PR: box#1282

[macroscopeapp]

Rename MetadataTaxonomiesManager.updateMetadataTaxonomyLevelById and update tests/docs while applying non-null assertions to path params across SDK URL builders

Introduce namespace in metadata template field options, rename Patch* types and method to Update*, and add ! non-null assertions to toString(...) path parameters throughout managers; extend metadata taxonomies test to update level 1 and verify template field options; update docs to reflect new names and usage.

📍Where to Start

Start with MetadataTaxonomiesManager.updateMetadataTaxonomyLevelById in metadataTaxonomies.ts, then review the test changes in metadataTaxonomies.test.ts and docs in metadataTaxonomies.md.

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Macroscope summarized 2b4535c.