[typespec-java] move from autorest.java into this repository

[XiaofeiCao]

• emitter: [Java] Move @azure-tools/typespec-java to typespec-azure repo  #4591
• PR CI
• release CI
• repo-related settings
• test
• sync sdk script
• customization-base (move to SDK repo?)
• nightly build
• skills

[XiaofeiCao]

First MVP be emitter+PR CI + test + release CI.
folder structure be:

• packages
  • typespec-java
    • emitter
    • emitter-tests

[timotheeguerin]

dup of #4225?

[XiaofeiCao]

dup of #4225?

Ah, yes. Closing his one.