[Mosaic] Fix infer/apply extensions.
1. For apply, llvm::StringMap()::insert(MapEntryTy*) will cause dangling reference if not constructing mlir::tpu::extensions::rules() with const-reference. However, if we do construct it with const-reference, the signature is not const-qualified and fails to compile. Hence, change it to llvm::StringMap()::insert(std::pair<...>) and get extension rules by const-reference.
2. Pass default tiling to infer rule, we need it to infer single op. See infer of tpu::MatmulOp.
PiperOrigin-RevId: 716274818
