Block Editor: Backport the initial set of block patterns from the Gutenberg Plugin.

[youknowriad]

This ticket tracks the backporting of the set of blocks patterns to load by default in Gutenberg Core.

While the design team still expects to make some final calls after beta1 about what block patterns to include/exclude. It is important to have an initial set ready for beta1.

Adding/Removing patterns after beta1 is fine since they don't have any impact on APIs or bug fixes but it is important that we're done before the string freeze to make sure these are translated properly.

Trac ticket: https://core.trac.wordpress.org/ticket/50550

[mcsf]

I left a question at ​https://github.com/WordPress/wordpress-develop/pull/385#discussion_r450117480. Regardless, this seems good to go.

[youknowriad]

In 48334:

Block Editor: Add the initial set of block patterns.

Included patterns:

text-two-columns
two-buttons
two-images
text-two-columns-with-images
text-three-columns-buttons
large-header
large-header-paragraph
three-buttons
quote
testimonials

Props mcsf, nrqsnchz.
See #50550.

[poena]

Are the testimonials meant to be included here? They were removed from the plugin.

[youknowriad]

Good catch @poena I did the patch before they were removed from the plugin, I can remove them here too for the moment.

[youknowriad]

In 48335:

Block Editor: Remove the Testimonials block pattern.

This ensures we have the same patterns used in the Gutenberg plugin.

Props poena.
See #50550.

[poena]

Require the title and content properties, add doing it wrong message.

[youknowriad]

In 48336:

Block Editor: Requires title and content when registering block patterns.

Props poena.
See #50550.

[desrosj]

In 48345:

Coding Standards: Correct two coding standards issues introduced in [48277] and [48334].

See #50504, #50550.

Trac ticket: https://core.trac.wordpress.org/ticket/50550

[youknowriad]

In 48639:

Block Editor: Update the Core Block Patterns.

Backport the latest block patterns from the Gutenberg plugin.
The new patterns adapt properly to Core themes.

Props nrqsnchz.
Fixes #50550, #50594.