[lldb/cmake] Enable more verbose find_package output.

Summary:
The purpose of this patch is to make identifying missing dependencies clearer to the user.
`find_package` will report if a package is not found, that output, combined with the exiting
status message, is clearer than not having the additional verbosity.

If the SWIG dependency is required {LLDB_ENABLE_PYTHON, LLDB_ENABLE_LUA}
and SWIG is not available, fail the configuration step.  Terminate the
configure early rather than later with a clear error message.

We could possibly modify:
`llvm-project/lldb/cmake/modules/FindPythonInterpAndLibs.cmake`
However, the patch here seems clear in my opinion.

Reviewers: aadsm, hhb, JDevlieghere

Reviewed By: JDevlieghere

Subscribers: labath, jrm, mgorny, lldb-commits

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D74917