[mlir] error out on unsupported attribute kinds in LLVM global translation

Some attribute kinds are not supported as "value" attributes of
`llvm.mlir.constant` when translating to LLVM IR. We were correctly reporting
an error, but continuing the translation using an "undef" value instead,
leading to a surprising mix of error messages and output IR. Abort the
translation after the error is reported.

Differential Revision: https://reviews.llvm.org/D75450