Add libclang dependency

[Galarius]

This pull request integrates several key updates and improvements to the build and workflow processes. Notably, a dependency on libclang has been introduced, and several refinements have been made to the build and release workflows.

libclang is a significant dependency, essential for implementing certain advanced language server features (e.g., #17, #48, kernel preprocessing). Unfortunately, there aren't any existing Conan 2.0-compatible recipes to incorporate it. As a result, it was decided to download prebuilt static libraries hosted by the Qt community. Cmake is responsible for the acquisition of the prebuilt static libraries during the configuration stage.

Details:

• Libclang Integration:

  • Introduced a new dependency on libclang.
  • Implemented caching for libclang to enhance build performance/cost when using GitHub actions.
  • The step to create a Conan package in the build workflow has been removed (there's no need for a packaged language server, and this step consumes considerable time).
  • The default build type has been set to Release, as prebuilt libclang static libraries are available only for the Release configuration and this is crucial on Windows. Other platforms will also default to the Release configuration, especially since the package creation step was eliminated.
  • [win32] Updated Windows conan profiles to use the dynamic "compiler.runtime" setting to avoid mismatches when linking to libclang. Moreover, prebuilt conan packages are available for this configuration.
  • [linux] Added the -no-pie linker flag because the prebuilt libclang static library is position-dependent.

• Other changes:

  • Addressed potential header inclusion problems by adding the missing #pragma once directive.