#824 Process source files in bulk: replace tabs with spaces, convert CRLF to LF, and trim trailing whitespaces as needed

All 3Ps include dirs are treated as SYSTEM, this will stop compilers
stop emitting warnings from those files and greatly helps having high
warning levels and not being swamped by warnings that come from
external libraries.

Rework cmake, the original plan was to maybe be able to use conan targets with the same name (that's why 3ps had names like apr::apr),
but it's safer and saner to put the LL 3ps under the ll:: prefix.
This also allows means it is possible to get rid of that bad "if( TRAGET ...) return() endif()" pattern and rather use include_guard().

Change projects to cmake targetsto get rid of havig to hardcore
include directories and link libraries in consumer projects.

Removing the change to LLPhysicsExtensions.cmake that was accidentally committed in changes set cf029fb1d6ee.

BUGFIX: Correcting a crash issue that was caused by the rebake navmesh callback handler unexpectedly changing the navmesh state.

PATH-181 and PATH-194: Implementing the building of the viewer with the stub library and validating that it does load/run as expected with the physics extensions disabled.

PATH-181 and PATH-194: Starting to put back the ability to build the viewer using the stub libraries.

First pass at using new llPhysicsExtensions library which
combines pathing and convex decomp.