[LoopInfo] Move generic LoopInfo into own files

This commit splits the generic part of `LoopInfo` into separate files.
These new `GenericLoopInfo` files are located in `llvm/Support` to be inline
with `GenericDomTree`.

Furthermore, this change ensures that MLIR's Bazel build does not have
to link against `LLVMAnalysis` just to use these template headers.

Depends on D148219

Reviewed By: ftynse

Differential Revision: https://reviews.llvm.org/D148235