export libxml2/2.12.6

[nikhalim]

Team is exploring using conanhelper to pull in libxml2 to replace tinyxml due to security vulnerabilities.
Instead of creating a new thirdpartyexport, we are recommending the team to use conanhelper to get the necessary libraries.

Specify library name and version: libxml2/2.12.6

---

• I've read the contributing guidelines.
• I've used a recent Conan client version close to the currently deployed.
• I've tried at least one configuration locally with the conan-center hook activated.

[nikhalim]

@ErikHons Created a new PR with the suggested naming scheme on the commit as I do not know how whether it's possible to rename an existing commit.