Tests: Add missing @covers tags for blocks, oembed, and rewrite tests

[sagarsdeshmukh]

What

Adds missing @covers annotations to 10 test classes across the blocks, oembed, and rewrite groups, as part of the ongoing effort in #64225.

blocks/

File	Annotation added
render.php	@covers ::do_blocks
renderReusable.php	@covers WP_Block
wpBlockParser.php	@covers WP_Block_Parser
wpBlockList.php	@covers WP_Block_List
registerBlockTypeFromMetadataWithRegistry.php	@covers ::register_block_type_from_metadata

oembed/

File	Annotation added
wpOembed.php	@covers WP_oEmbed
WpEmbed.php	@covers WP_Embed
postEmbedUrl.php	@covers ::get_post_embed_url

rewrite/

File	Annotation added
permastructs.php	@covers ::add_permastruct, @covers ::remove_permastruct
numericSlugs.php	@covers ::url_to_postid

Why

Without @covers, PHPUnit cannot correctly attribute code coverage to the functions and classes under test. This leads to inaccurate coverage reports on Codecov, where a function may appear uncovered even when dedicated tests exist for it.

Testing

Ran all 10 affected test classes locally:

npm run test:php -- --filter 
"Tests_Blocks_Render|Tests_Blocks_RenderReusable|Tests_Blocks_wpBlockParser| 
Tests_Blocks_wpBlockList|Tests_Blocks_RegisterBlockTypeFromMetadataWithRegistry| 
Tests_WP_oEmbed|Tests_WP_Embed|Tests_Post_Embed_URL|
Tests_Rewrite_Permastructs|Tests_Rewrite_NumericSlugs"

OK (234 tests, 330 assertions) 

Trac

Follow-up to [62213], [62218], [62222].

Fixes https://core.trac.wordpress.org/ticket/64225

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