Remove unnecessary IntermediateSnapshotNode and EmptySnapshotConfig

[gshank]

resolves #10326

Problem

We no longer need the IntermediateSnapshotNode and EmptySnapshotConfig classes, or the IntermediateNode typevar.

Solution

Remove them.

Checklist

• I have read the contributing guide and understand what's expected of me
• I have run this code in development and it appears to resolve the stated issue
• This PR includes tests, or tests are not required/relevant for this PR
• This PR has no interface changes (e.g. macros, cli, logs, json artifacts, config files, adapter interface, etc) or this PR has already received feedback and approval from Product or DX
• This PR includes type annotations for new and modified functions

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.78%. Comparing base (71a8a41) to head (7853431).

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #10332      +/-   ##
==========================================
- Coverage   88.83%   88.78%   -0.06%     
==========================================
  Files         180      180              
  Lines       22490    22479      -11     
==========================================
- Hits        19980    19958      -22     
- Misses       2510     2521      +11     

Flag	Coverage Δ
integration	86.08% <100.00%> (-0.11%)	⬇️
unit	62.17% <100.00%> (-0.02%)	⬇️

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[MichelleArk]

why is this no longer necessary?

[gshank]

It was converting from an IntermediateSnapshotNode to a SnapshotNode. The original point of the IntermediateSnapshotNode was that it wouldn't require the validations that we do on a SnapshotNode (but I think that actually broke quite a while back). I recently did the ticket to move validation of SnapshotNodes to a post-parsing step. So we definitely don't need the IntermediateSnapshotNode anymore.