[Tracking Issue] Introducing DeclBuffer

[vinx13]

This issue is to track progress for the RFC Introducing DeclBuffer

• Introduce DeclBuffer data structure, add corresponding visitors in IR functors. [TIR] Add DeclBuffer IR node and functors #12300
• Update TVMScript syntax for T.decl_buffer and T.allocate [TIR, TVMScript] Update printer / parser to make T.allocate return buffer var #12412
• Refactor existing passes and test cases to use DeclBuffer.
• Enforce the usage of DeclBuffer. No implicit buffer declarations are allowed.

[tqchen]

@vinx13 seems we can close this?

[vinx13]

There are some items to be done, usage of DeclBuffer hasn't been enforced

[tqchen]

Get it, would be good to get it sometime when we have cycles