Remove unused storage callbacks

[magnetised]

Now that SQLite has all the shape data we don't need the storage callbacks that retreive it, and also do not need to serialize the shape to disk at all.

I've kept the get_all_stored_shape_handles/1 callback to allow for some kind of async reconciliation process that can detect and remove orphaned storage instances.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 87.31%. Comparing base (ba6dd2c) to head (8a381da).
⚠️ Report is 1 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3717      +/-   ##
==========================================
- Coverage   87.36%   87.31%   -0.05%     
==========================================
  Files          23       23              
  Lines        2011     2011              
  Branches      528      529       +1     
==========================================
- Hits         1757     1756       -1     
- Misses        252      253       +1     
  Partials        2        2              

Flag	Coverage Δ
packages/experimental	87.73% <ø> (ø)
packages/react-hooks	86.48% <ø> (ø)
packages/start	82.83% <ø> (ø)
packages/typescript-client	93.39% <ø> (-0.08%)	⬇️
packages/y-electric	56.05% <ø> (ø)
typescript	87.31% <ø> (-0.05%)	⬇️
unit-tests	87.31% <ø> (-0.05%)	⬇️

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