[ELF] Define a reportRangeError() overload for thunks and tidy up recent PPC64 thunk range errors

Prefer `errorOrWarn` to `fatal` for recoverable errors and graceful degradation
when --noinhibit-exec is specified.

Mention the destination symbol, otherwise the diagnostic is not really actionable.
Two errors are not tested but the patch does not intend to add the coverage.

Reviewed By: grimar

Differential Revision: https://reviews.llvm.org/D87486