3210-refactor-libutil-misc

Closes #3210.

• 76d0eeaa add ability to format changed files

• 7492ac1b properly match header names with regex

• 2254edc0 refactor file utilities

  • Unify filename.h and file_utilities.h under filesystem.h.
  • Rename Filename class to Path since it more accurately represents it.
  • Make its interface as close as possible to that of std::filesystem::path.
  • Remove unused method expandWithDefault.
  • Rename useAsDefault to replaceExtension since it was only used in the purpose of replacing extension.
  • Unroll the split method in the constructor.

• 18613aec refactor io utilities

  • Rename util/io_utilities.h to util/io.h to escape redundancy.
  • Create readUint and writeUint templates.
  • Use reverse_copy for potential performance boost.
  • Add missing unit tests.

• a6169986 refactor string utilities

  • Rename util/strutil.h to util/str.h to escape redundancy.
  • Simplify trim function.
  • Remove unused functions.
  • Get rid of the regex conditional compilation that helped Kea build with ancient compilers. Lack of proper regex functionality now results in failure in configure.ac.

• 2d205f44 miscellaneous warning fixes in lib/util

  • Wsign-compare
  • Wshadow
  • doxygen warnings
  • fix compilation for src/lib/util/tests/Makefile.am

• 4a147743 update copyright dates

• dceee6cd clean up some header includes

• a71cda1e fix some warnings

• 6ebc7533 fix different exception message on BSD