[mlir] Improve LLVM shlib support

mlir-tblgen was incompatible with libLLVM, due to explicit linkage with
libLLVMSupport etc.
As it cannot link with libLLVM, make sure all lib it uses are not using libLLVM
either.

As a side effect, also remove some explicit references to LLVM libs and use
components instead.

Differential Revision: https://reviews.llvm.org/D88846