[mlir][ABI] Add writable, dead_on_unwind, dead_on_return, nofpclass param attrs to LLVM dialect (#188374)
The MLIR LLVM dialect is missing support for several parameter
attributes that
exist in LLVM IR: `writable`, `dead_on_unwind`, `dead_on_return`, and
`nofpclass`. This adds them to the kind-to-name mapping in
`AttrKindDetail.h`
and the corresponding name accessors in `LLVMDialect.td`.
The existing generic conversion infrastructure in `ModuleTranslation`
and
`ModuleImport` picks them up automatically — `writable` and
`dead_on_unwind`
round-trip as `UnitAttr`, while `dead_on_return` and `nofpclass`
round-trip as
`IntegerAttr`.
CIR needs these to match classic codegen's ABI output (sret gets
`writable
dead_on_unwind`, indirect args get `dead_on_return`, fast-math FP args
get
`nofpclass`).