Gutenberg Blocks: Rename o2 preset to p2

[ockham]

Quoting D19603-code #394021

I'd originally meant to call the preset p2 (since that's what most of us intuitively refer to, not o2). However, for automated namespacing of generated CSS, I changed that to o2, since the body element of P2s already had an o2 class (but not a p2 one) -- it was simply more convenient at the time not to add another class.

However, as of #26662, we're no longer auto-namespacing CSS with block/preset names anyway. I meant to rename the preset on the Calypso set for a while (and will proceed to do so now). This phab diff is a good opportunity to also do so on the server side.

Testing instructions

Verify that npm run sdk -- gutenberg client/gutenberg/extensions/presets/p2/ successfully builds files in that folder's build/ subdirectory.

[matticbot]

Test live: https://calypso.live/?branch=rename/preset-o2-to-p2

[ghost]

That's a great PR description, thank you so much for your effort!

Generated by 🚫 dangerJS

[ockham]

Once this is merged, let's have CircleCI build this preset for us.

[tyxla]

Nice 👍

Seems like we still refer to p2s as to it as o2s here and there though...

[dmsnell]

Not a fan of this since the actual theme that this injects into is called o2, plus it's changing things and I don't see a benefit. But whatever. Just saying it seems like a regression to me.

[ockham]

Not a fan of this since the actual theme that this injects into is called o2, plus it's changing things and I don't see a benefit. But whatever. Just saying it seems like a regression to me.

I don't feel super strong about this, so I'm willing to cede this PR. It just seemed to me that we're almost exclusively using 'P2' to refer to those...

[simison]

We can prolly close this one.