Consolidate typing for coords using Coords and StrongCoords aliases

[aman-coder03]

Fixes #7972
Earlier opened a PR #7987

This PR consolidates the typing of coords across the codebase by introducing explicit type aliases:

• CoordValue
• Coords
• StrongCoordValue
• StrongCoords

These follow the existing pattern used for Shape, Dims, and StrongDims in shape_utils.py.

Previously, coords were inconsistently typed across modules (e.g. Sequence, Sequence | np.ndarray, dict[str, Any]), which made downstream typing unclear and less consistent. This PR standardizes both the user-facing and normalized/internal representations.

Additionally:

• Adjusted related typing in model.core, shape_utils, and the ArviZ backend
• Resolved a circular import encountered during initial refactor
• Updated relevant tests accordingly

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[aman-coder03]

@michaelosthege i have re-opened this PR which was earlier #7987

[aman-coder03]

@ricardoV94 can you please assign a label to this PR

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.30%. Comparing base (11d0f1b) to head (6fcb9fa).
⚠️ Report is 8 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #8094      +/-   ##
==========================================
- Coverage   90.89%   89.30%   -1.60%     
==========================================
  Files         123      123              
  Lines       19501    19549      +48     
==========================================
- Hits        17726    17458     -268     
- Misses       1775     2091     +316     

Files with missing lines	Coverage Δ
pymc/backends/arviz.py	96.19% <100.00%> (+0.15%)	⬆️
pymc/distributions/distribution.py	94.50% <100.00%> (ø)
pymc/distributions/shape_utils.py	91.35% <100.00%> (-0.53%)	⬇️
pymc/model/core.py	94.23% <100.00%> (+0.92%)	⬆️
pymc/printing.py	87.66% <100.00%> (+0.16%)	⬆️
pymc/step_methods/state.py	95.52% <100.00%> (ø)
pymc/util.py	82.23% <100.00%> (+1.12%)	⬆️

... and 9 files with indirect coverage changes

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[aman-coder03]

@ricardoV94 please have a look at this PR!