$args taking effect too late in register_block_type_from_metadata

[aristath]

The register_block_type_from_metadata function accepts 2 arguments:

• $file_or_folder
• $args

The $file_or_folder is a path the the block.json file, or the folder containing it. $args is an array of arguments that can be passed to the function in order to provide complimentary data.
The problem right now is that $args are parsed too late: They get parsed after the scripts/styles have been registered, after all other calculations have been completed, right before we call WP_Block_Type_Registry::get_instance()->register();.
The problem with the current approach is that $args are unable to register script/styles, or even be used to take part in all the processing that the register_block_type_from_metadata function does.
As a side-effect, it's impossible to register a block by passing an array of arguments, without the presence of a block.json file.

Trac ticket: https://core.trac.wordpress.org/ticket/56865

[audrasjb]

As per today's bug scrub, self assigning for review

[mukesh27]

This ticket was discussed in the bug scrub.

THe PR need some manual testing.

Additional props @costdev

[costdev]

The PR could also use a unit test to ensure that it's now possible to register a block by passing an array of arguments, without the presence of a block.json file, and is protected going forward.

As this still needs some work, I'm moving this to the 6.3 milestone. If testing and unit tests are ready before RC1, feel free to pull this ticket back into the 6.2 milestone for commit consideration.

Added PHPUnit tests and fixed issues that surfaced from said tests.