Convert a Classic Block into Multiple Blocks

[mtias]

Let's leverage the pasting instructions we have for converting WordPress content into blocks, to add an action to the "Classic Block" that would transform a single legacy post into multiple blocks:

[aduth]

Related: #2454, #2617

[ephox-mogran]

This might be the kind of action that you may want a preview for (before it executes). Allow the user to see how the block identification is going to work, or whether they will lose a lot of their content.

[vedranmiletic]

This is available (at least) in 1.7.0, but YouTube embed gets lost during conversion. Is that a known issue? I know this is rather specific issue; I tried searching before reporting this, but found nothing related.

[aduth]

Should this be closed by #3179?

Maybe creating a separate issue for the problem described by @vedranmiletic in #3149 (comment).

[ellatrix]

@vedranmiletic This should be fixed by #3326 in the next version.

[vedranmiletic]

@iseulde Wow, before I even reported it. Thanks!