[MLIR][OpenMP] Improve assemblyFormat handling for clause-based ops (#108023)

This patch modifies the representation of `OpenMP_Clause` to allow
definitions to incorporate both required and optional arguments while
still allowing operations including them and overriding the
`assemblyFormat` to take advantage of automatically-populated format
strings.

The proposed approach is to split the `assemblyFormat` clause property
into `reqAssemblyFormat` and `optAssemblyFormat`, and remove the
`isRequired` template and associated `required` property. The
`OpenMP_Op` class, in turn, populates the new `clausesReqAssemblyFormat`
and `clausesOptAssemblyFormat` properties in addition to
`clausesAssemblyFormat`. These properties can be used by clause-based
OpenMP operation definitions to reconstruct parts of the
clause-inherited format string in a more flexible way when overriding
it.

Clause definitions are updated to follow this new approach and some
operation definitions overriding the `assemblyFormat` are simplified by
taking advantage of the improved flexibility, reducing code duplication.
The `verify-openmp-ops` tablegen pass is updated for the new
`OpenMP_Clause` representation.

Some MLIR and Flang unit tests had to be updated due to changes to the
default printing order of clauses on updated operations.

0 files changed, 0 insertions, 0 deletions