Residual of block found in `get_blocks_metadata` even when block is unregistered using `unregister_block_type()`.

[thekt12]

The get_blocks_metadata() function retrieves all registered blocks using WP_Block_Type_Registry::get_all_registered(). It updates its internal static variable with new blocks but does not account for blocks that have been unregistered. Consequently, residual blocks remain in the static variable and are processed in functions consuming get_blocks_metadata(), such as wp_add_global_styles_for_blocks. This oversight can lead to unnecessary processing overhead.

POC for 61405

Trac ticket: https://core.trac.wordpress.org/ticket/61405