Restructure CompilationConfig, add HardwareDescription

Explanation of changes

• Restructures the CompilationConfig by introducing the hardware_compilation_config
• The hardware_compilation_config contains the backend, the hardware_descriptions, the hardware_options, and connectivity (which may contain an old-style hardware config)
• The new hardware_descriptions datastructure stores the description of the control hardware instruments (such as hardware_type, high-level settings).
• Updates documentation to reflect this new structure of the CompilationConfig

Motivation of changes

Part of &1 (closed)

This MR makes sure that config information corresponding to the "circuit_to_device compilation" and "hardware compilation" are grouped separately. After this MR, the old-style hardware config dict now only contains connectivity informations, which we can transfer to the new Connectivity datastructure in a follow-up MR.

Still to do

• Make sure the documentation (clearly) reflects this structure
• Double-check all CompilationConfig (sub)datastructures docstrings
• Add _import_backend_if_str validator to HardwareCompilationConfig
• Decide which fields in HardwareCompilationConfig should be Optional
• Make sure compiling with an (deprecated) old-style hardware works and is covered by some tests
• Bump CompilationConfig version
• Double-check if using Annotated type is best option to discriminate between HardwareDescription classes

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Merge checklist

See also merge request guidelines

• Merge request has been reviewed (in-depth by a knowledgeable contributor), and is approved by a project maintainer.
• New code is covered by unit tests (or N/A).
• New code is documented and docstrings use numpydoc format (or N/A).
• New functionality: considered making private instead of extending public API (or N/A).
• Public API changed: added @deprecated (or N/A).
• Tested on hardware (or N/A).
• CHANGELOG.md and AUTHORS.md have been updated (or N/A).
• Windows tests in CI pipeline pass (manually triggered by maintainers before merging).

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