Adding local boost support to CMake configuration.

[lsawade]

Description

Added CMake feature to look for local boost.

If boost>=1.73.0 is installed and $BOOST_ROOT is cmake will look for as well as the necessary components. If the necessary components cannot be found, cmake will install

On Della:

# in addition to other compiler modules:
module load boost/1.73.0

cmake3 -S . -B build_cpu
cmake3 --build build_cpu -j

Issue Number

Partially fixes #63

Checklist

Please make sure to check developer documentation on specfem docs.

• [x] I ran the code through pre-commit to check style
• [x] My code passes all the integration tests
• [ ] ~I have added sufficient unittests to test my changes~
• [x] I have added/updated documentation for the changes I am proposing
• [x] I have updated CMakeLists to ensure my code builds
• [ ] My code builds across all platforms? CAN I TEST THIS?

[buildbot-princeton]

Can one of the admins verify this patch?

[buildbot-princeton]

Can one of the admins verify this patch?

[Rohit-Kakodkar]

ok to test

[Rohit-Kakodkar]

ok to test