[mlir] Declare promised interfaces for the ConvertToLLVM extension (#76341)

This PR adds promised interface declarations for
`ConvertToLLVMPatternInterface` in all the dialects that support the
`ConvertToLLVM` dialect extension.

Promised interfaces allow a dialect to declare that it will have an
implementation of a particular interface, crashing the program if one
isn't provided when the interface is used.