Add optional fetch_content support for needed Boost libraries

[hkaiser]

In addition to #3440, we should add a build system option that fetches the needed Boost libraries from github instead of relying on an installed version. This shouldn't be too hard as we don't rely on any built Boost Libraries, all we need is header only.

[gonidelis]

Please revise the related GSoC project and make any changes needed.

@NK-Nikunj too.

https://github.com/STEllAR-GROUP/hpx/wiki/Google-Summer-of-Code-(GSoC)-2022#improve-build-system-usability-by-adding-fetching-options-on-hpx-dependencies

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[hkaiser]

Intrinsic CMake support in Boost reaches complete status starting V1.82: https://github.com/boostorg/cmake/blob/develop/README.md. At that point this ticket should be easily resolvable.

[SAtacker]

Intrinsic CMake support in Boost reaches complete status starting V1.82: https://github.com/boostorg/cmake/blob/develop/README.md. At that point this ticket should be easily resolvable.

This can be accomplished in the current boost versions as well.
PTAL at following example:

https://github.com/SAtacker/quick-ftxui/blob/40e7a49bb9fd53f23a3fd1a7779411513c0e4c32/CMakeLists.txt#L16-L38

CC @gonidelis @hkaiser