Adds the JSX transformer

[rbuckton]

The JSX transformer is designed to transform JSX-specific syntax into compatible JavaScript when the --jsx react compiler option.

Related Pull Requests:

• Adds the visitor API foundation for tree transformations. #6892 - Adds the visitor API foundation for tree transformations.
• Adds the Transform Flags concept for tree transformations #6983 - Adds the Transform Flags concept for tree transformations.
• Adds the transformFiles API for tree transformations #6986 - Adds the transformFiles API for tree transformations.
• Adds a simplified pretty printer for tree transformations #6987 - Adds a simplified pretty printer for tree transformations.
• Adds the TypeScript transformer #7191 - Adds the TypeScript transformer.
• Adds the JSX transformer #7192 - Adds the JSX transformer.
• Adds the ES7 transformer #7193 - Adds the ES7 transformer.
• Adds the ES6 transformer #7194 - Adds the ES6 transformer.
• Adds the Module transformers #7206 - Adds the Module transformer.

[RyanCavanaugh]

Am I reading this correctly that there are zero baseline changes?

[rbuckton]

@RyanCavanaugh With only these transformations, the emitter isn't far enough along to run the tests and capture baseline changes. Those will come after I submit the last PR containing the module transformer.

[sandersn]

I don't think this temp is needed for readability or efficiency.

[sandersn]

👍