[flang][fir][NFC] Move ShapeType to TableGen type definition

This is the first patch of a serie to move FIR types to TableGen format as suggested in D96172.
This patch is setting up the files for FIR types and move the ShapeType to TableGen.

As discussed with @schweitz, I'm taking over this task to help the FIR upstreaming effort.

Reviewed By: mehdi_amini

Differential Revision: https://reviews.llvm.org/D96422