FindBoost: Add support for Boost 1.88

Update the list of known versions.

Run the command

    cmake -DBOOST_DIR=/path/to/boost_1_88_0 \
      -P Utilities/Scripts/BoostScanDeps.cmake

to extract dependencies from the 1.88.0 source tree.

Dependencies differ from 1.87:

* Boost.Process now depends on Boost.Filesystem

Signed-off-by: Kefu Chai <tchaikov@gmail.com>