[CMake] Replace deprecated `FindPythonInterp` module

[guitargeek]

See: https://cmake.org/cmake/help/latest/module/FindPythonInterp.html

Sister PR of https://github.com/root-project/root/pull/15420.

[phsft-bot]

Starting build on ROOT-performance-centos8-multicore/soversion, ROOT-ubuntu2204/nortcxxmod, ROOT-ubuntu2004/python3, mac12arm/cxx20, windows10/default How to customize builds

[phsft-bot]

Build failed on ROOT-ubuntu2204/nortcxxmod. Running on root-ubuntu-2204-1.cern.ch:/home/sftnight/build/workspace/roottest-pullrequests-build See console output.

Errors:

• [2024-05-07T00:00:57.548Z] /home/sftnight/build/workspace/roottest-pullrequests-build/root/interpreter/cling/lib/Interpreter/IncrementalParser.cpp:979:19: error: ‘SM’ was not declared in this scope; did you mean ‘S’?
• [2024-05-07T00:00:57.548Z] /home/sftnight/build/workspace/roottest-pullrequests-build/root/interpreter/cling/lib/Interpreter/IncrementalParser.cpp:979:36: error: ‘PP’ was not declared in this scope

[phsft-bot]

Build failed on ROOT-ubuntu2004/python3. Running on root-ubuntu-2004-1.cern.ch:/home/sftnight/build/workspace/roottest-pullrequests-build See console output.

Errors:

• [2024-05-07T00:00:41.700Z] FAILED: interpreter/cling/lib/Interpreter/CMakeFiles/obj.clingInterpreter.dir/IncrementalParser.cpp.o
• [2024-05-07T00:00:41.700Z] /home/sftnight/build/workspace/roottest-pullrequests-build/root/interpreter/cling/lib/Interpreter/IncrementalParser.cpp:979:19: error: ‘SM’ was not declared in this scope; did you mean ‘S’?
• [2024-05-07T00:00:41.700Z] /home/sftnight/build/workspace/roottest-pullrequests-build/root/interpreter/cling/lib/Interpreter/IncrementalParser.cpp:979:36: error: ‘PP’ was not declared in this scope

[phsft-bot]

Build failed on ROOT-performance-centos8-multicore/soversion. Running on olbdw-01.cern.ch:/data/sftnight/workspace/roottest-pullrequests-build See console output.

Errors:

• [2024-05-07T00:05:00.893Z] /data/sftnight/workspace/roottest-pullrequests-build/root/interpreter/cling/lib/Interpreter/IncrementalParser.cpp:979:19: error: ‘SM’ was not declared in this scope
• [2024-05-07T00:05:00.893Z] /data/sftnight/workspace/roottest-pullrequests-build/root/interpreter/cling/lib/Interpreter/IncrementalParser.cpp:979:36: error: ‘PP’ was not declared in this scope

[phsft-bot]

Build failed on mac12arm/cxx20. Running on 194.12.161.128:/Users/sftnight/build/workspace/roottest-pullrequests-build See console output.

Errors:

• [2024-05-07T00:13:50.250Z] FAILED: interpreter/cling/lib/Interpreter/CMakeFiles/obj.clingInterpreter.dir/IncrementalParser.cpp.o
• [2024-05-07T00:13:50.586Z] /Users/sftnight/build/workspace/roottest-pullrequests-build/root/interpreter/cling/lib/Interpreter/IncrementalParser.cpp:979:19: error: use of undeclared identifier 'SM'
• [2024-05-07T00:13:50.586Z] /Users/sftnight/build/workspace/roottest-pullrequests-build/root/interpreter/cling/lib/Interpreter/IncrementalParser.cpp:979:36: error: use of undeclared identifier 'PP'
• [2024-05-07T00:13:50.586Z] /Users/sftnight/build/workspace/roottest-pullrequests-build/root/interpreter/cling/lib/Interpreter/IncrementalParser.cpp:982:14: error: use of undeclared identifier 'PP'

[phsft-bot]

Build failed on windows10/default. Running on null:C:\build\workspace\roottest-pullrequests-build See console output.

Errors:

• [2024-05-07T00:35:23.456Z] C:\build\workspace\roottest-pullrequests-build\root\interpreter\cling\lib\Interpreter\IncrementalParser.cpp(979,1): error C2065: 'SM': undeclared identifier [C:\build\workspace\roottest-pullrequests-build\build\interpreter\cling\lib\Interpreter\obj.clingInterpreter.vcxproj]
• [2024-05-07T00:35:23.456Z] C:\build\workspace\roottest-pullrequests-build\root\interpreter\cling\lib\Interpreter\IncrementalParser.cpp(979,1): error C2065: 'PP': undeclared identifier [C:\build\workspace\roottest-pullrequests-build\build\interpreter\cling\lib\Interpreter\obj.clingInterpreter.vcxproj]
• [2024-05-07T00:35:23.456Z] C:\build\workspace\roottest-pullrequests-build\root\interpreter\cling\lib\Interpreter\IncrementalParser.cpp(982,1): error C2065: 'PP': undeclared identifier [C:\build\workspace\roottest-pullrequests-build\build\interpreter\cling\lib\Interpreter\obj.clingInterpreter.vcxproj]