Initial PProc mono repo

[jinmannwong]

Description

• Created pproc-runtime and pproc-core
• Migrated earthkit-workflows-pproc into pproc-core
• Started migration of functionality from pproc into pproc-core and pproc-runtime for the computation of ensms, prob, quantiles and thermal indices
• Minimal changes to PProc itself, to avoid too many conflicts with ongoing developments

Changes made in ppcore/schema that differ from pproc/schema:

• Support for externally provided forecast definitions are allowed, as well as named definitions in the schema itself
• Selection of inputs required is now handled by qube
• New exception classes to allow easier identification of schema where error has occured

Contributor Declaration

By opening this pull request, I affirm the following:

• All authors agree to the Contributor License Agreement.
• The code follows the project's coding standards.
• I have performed self-review and added comments where needed.
• I have added or updated tests to verify that my changes are effective and functional.
• I have run all existing tests and confirmed they pass.