Work on MCPL 2.0.0

[tkittel]

Main features would be:

• Support Windows.
• Have complete Python wheels on PyPI (e.g. also libmcpl.so, mcpltool, mcpl-config, CMake files).
• Revamp packaging (e.g. mcpl/mcpl-core/mcpl-python/mcpl-phits/mcpl-ssw/mcpl-geant4 packages).
• Restructure repo so all development is in one repo, no upstream at ESS => we can do proper PRs etc.
• Vastly increase CI coverage.

[tkittel]

Issues that we will try to fix for release 2.0.0:

• MSVC build #75
• Print MCPL cmake options #69
• enable github discussions #76
• More platforms in github actions CI #66
• Embedded zlib compression looks like it is not fully portable  #59
• MCPL file is crushing when attepting to simulate Mcstas instrument with big statistics on Windows. #57
• Use 64bit versions of ftell and friends #10

Things NOT in scope (but still something we want to do at a later point):

• Python API write capability (write capability in Python API #54 Python writer for MCPL files #70)
• Make mcpl-extra tools public (Feature request: Enable filtering options in the non-DG framework mcpltool #44)
• Extra "userdata" fields of arbitrary size (Optionally support user data of arbitrary size. #60)

[tkittel]

FYI @willend