[mlir] Move casting method calls to function calls

The MLIR classes Type/Attribute/Operation/Op/Value support
cast/dyn_cast/isa/dyn_cast_or_null functionality through llvm's doCast
functionality in addition to defining methods with the same name.
This change continues the migration of uses of the method to the
corresponding function call as has been decided as more consistent.

This commit attempts to update all occurrences of the casts in .td
files, although it is likely that a couple were missed.

Context:
- https://mlir.llvm.org/deprecation/ at "Use the free function variants for dyn_cast/cast/isa/…"
- Original discussion at https://discourse.llvm.org/t/preferred-casting-style-going-forward/68443

Implementation:
Unfortunatley, this was not automated, but was handled by mindlessly
going to next occurrences of patterns, selecting the piece of code to
be moved into the function call, and running a vim macro over the span
of around 4 hours.

Differential Revision: https://reviews.llvm.org/D150199