Blocks: Fix wrapper attribute merging in `get_block_wrapper_attributes()`.

Replace the previous generic concatenation logic in `get_block_wrapper_attributes()` with attribute-specific merge behavior:

- Add explicit merge callbacks for each attribute.
- Merge style values safely, normalize trailing semicolons, and sanitize the result.
- Merge class values with deduplication .
- Treat id and aria-label as override attributes, giving precedence to explicitly passed extra attributes.

Props adrock42, mamaduka, r1k0, westonruter, wildworks.

Fixes #64603.

git-svn-id: https://develop.svn.wordpress.org/trunk@62068 602fd350-edb4-49c9-b593-d223f7449a82