[mlir][Tosa] Include generated interface declarations outside of namespaces (#236103)
`TosaInterfaces.h.inc` was included from within `namespace mlir::tosa`,
relying on the interfaces in `TosaInterfaces.td` having an empty
`cppNamespace`. The interfaces now specify `cppNamespace =
"::mlir::tosa"` and the generated header is included at global scope.
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Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>