[Feature] Structural Refactor for Execute

[MJC598]

What does this PR do?

Quite a lot:

• Restructured package layout to contain only one subpackage (respondpy.data)
• Broke out exposed components in __init__.py more effectively to manage imports from language bindings
• Added new handling for incomplete transition matrices and state vectors
• Redid testing for new layout
• Implemented a new Input class wrapper to help support SQLite and Config files
• Implemented a wrapper Parameter class around the enum to better reduce redundant strings
• Implemented better memory caching to avoid repeated I/O from the database
• Bumped version to next minor patch (0.1.3 -> 0.2.0)

What Wrike task is this associated with?

• In my defense, it started here: https://www.wrike.com/open.htm?id=4469957287

Checklist before merging

• If adding a core feature, I've added related tests.
• This is part of a product update, and I've added an explanation of what is different to the changelog.

[codecov]

Codecov Report

❌ Patch coverage is 97.73585% with 12 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/respondpy/data/transition_matrices.py	90.74%	10 Missing ⚠️
src/respondpy/data/input.py	98.83%	2 Missing ⚠️

Files with missing lines	Coverage Δ
src/respondpy/__init__.py	100.00% <100.00%> (+6.25%)	⬆️
src/respondpy/_utils.py	100.00% <100.00%> (ø)
src/respondpy/cost_effectiveness.py	100.00% <100.00%> (ø)
src/respondpy/data/__init__.py	100.00% <100.00%> (ø)
src/respondpy/data/database_helpers.py	100.00% <100.00%> (ø)
src/respondpy/data/logic_conditions.py	100.00% <100.00%> (ø)
src/respondpy/data/parameters.py	100.00% <100.00%> (ø)
src/respondpy/data/state_vectors.py	100.00% <100.00%> (ø)
src/respondpy/history.py	100.00% <100.00%> (ø)
src/respondpy/model.py	100.00% <100.00%> (ø)
... and 4 more

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