Bedrock: Move template parts from patterns to templates

[iamtakashi]

Changes proposed in this Pull Request:

I'm not sure when, but with a recent change in the Gutenberg plugin, having a template part in a pattern seems to break the editor. Therefore, I moved all the template parts from the patterns and added to the templates directly.

Related issue(s):

This should fix https://github.com/Automattic/wp-calypso/issues/88219