Accessibility fix, switch attribute from "lang" to "data-lang"

[mkaz]

• Uses commits from @CarlosLongarela that change the attributs.
• Adds a deprecated property to the block

IN PROGRESS

This PR does not work as expected, if using an older block with the "lang" attribute, the deprecation does not get run and the attribute does not get read or converted properly.

To test:

• Create a post with the trunk version of the block, add a code block with language
• Apply the PR, and rebuild
• Open the post in the Editor and the block is invalidated

[mkaz]

I've determined the cause of why this deprecation is not working and filed a ticket at: https://github.com/WordPress/gutenberg/issues/33672