Blocks should be able to use itself as a child block target in schemas

[aswamy]

Describe the bug

• Block type completion should not allow itself as a completion option

• Theme check should warn us when we try to use a block within itself

• Bonus: Should we also warn when we see a circular block dependency?

Source

Expected behaviour

• blocks and presets.[].blocks.[].type should not include itself as an option
• theme check should warn us when a block uses itself as a child block in its schemas

Actual behaviour

• vscode completion offers the block itself as an option
• no theme check error

[aswamy]

@charlespwd This is the circular issue i was talking about. Should i just close this since we should be able to do this?