[tclap] Add CMake package config and exported target for 1.2.5

[miyanyan]

• Changes comply with the maintainer guide.
• SHA512s are updated for each updated download.
• The "supports" clause reflects platforms that may be fixed by this new version, or no changes were necessary.
• Any fixed CI baseline and CI feature baseline entries are removed from that file, or no entries needed to be changed.
• All patch files in the port are applied and succeed.
• The version database is fixed by rerunning ./vcpkg x-add-version --all and committing the result.
• Exactly one version is added in each modified versions file.

the CMakeLists.txt file is copied from tclap 1.4 version, with vcpkg-specific adjustments for header-only layout and config placement, see https://github.com/DAarno/tclap/blob/1.4/CMakeLists.txt, https://github.com/DAarno/tclap/blob/1.4/include/tclap/CMakeLists.txt

currently I can't update tclap to 1.4 as ecal only support tclap 1.2.5, this pr can solve the tclap problems in #49552

[JavierMatosD]

Vendoring upstreams build system is typically discouraged. On top of that tclap's website states that version 1.4 is the recommended version for new projects. 1.2 only gets critical bug fixes. There's no good reason to stay on 1.2.5. If ecal only supports tclap 1.2.5, that's something to fix upstream in ecal

[miyanyan]

ecal will drop tclap in 6.2, maybe the best approach is waiting for the new release, eclipse-ecal/ecal#2518