[expat] Fix build failure.

[Hoikas]

This fixes a build failure in the expat port due to VERSION no longer being set in the portfile. This was broken by #27547. I elected to hardwire the version numbers instead of reading vcpkg.json because vcpkg.json can have versions that are not expat versions, eg version-date.

• What does your PR fix?

  Fixes

CMake Error at D:/Plasma/CyanWorlds.comEngine/build/vc++2022-x64/vcpkg_installed/x64-windows-plasma/share/vcpkg-cmake-config/vcpkg_cmake_config_fixup.cmake:36 (message):

  
  'D:/Plasma/CyanWorlds.comEngine/vcpkg/packages/expat_x64-windows-plasma/debug/lib/cmake/expat-'
  does not exist.
Call Stack (most recent call first):
  ports/expat/portfile.cmake:26 (vcpkg_cmake_config_fixup)
  scripts/ports.cmake:147 (include)



error: building expat:x64-windows-plasma failed with: BUILD_FAILED

• Which triplets are supported/not supported? Have you updated the CI baseline?

  No change

• Does your PR follow the maintainer guide?

  Yes

• If you have added/updated a port: Have you run ./vcpkg x-add-version --all and committed the result?

  Yes

If you are still working on the PR, open it as a Draft: https://github.blog/2019-02-14-introducing-draft-pull-requests/

[dg0yt]

No. Add this add at the top (until it arrives in a central place):

vcpkg_minimum_required(VERSION 2022-10-12) # for ${VERSION}

It will tell you if your vcpkg tool is too old.

And use string(REPLACE ...) to transform the version to the git tag.

[Osyotr]

Hmm I thought it will be fixed in #27598

[dg0yt]

expat was missing. However, the CMake 3.25.1 PR has the general update.

[Hoikas]

Thanks for the tip. I've updated the PR to use the new functionality.

[JavierMatosD]

Thank you!