fix: ensure log store correctly identifies existing delta tables

[rtyler]

If a process fails before the initial commit is able it's possible for _commit(.*).tmp to be placed inside _delta_log/ and then a subsequent attempt to the create the delta table will fail because the log store believes it has been created but no initial transaction exists.

Sponsored-by: Scribd Inc.

[codecov]

Codecov Report

Attention: Patch coverage is 83.87097% with 5 lines in your changes missing coverage. Please review.

Project coverage is 72.41%. Comparing base (55a19f6) to head (8d85f3a).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/core/src/logstore/mod.rs	86.66%	1 Missing and 3 partials ⚠️
crates/core/src/storage/mod.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2890      +/-   ##
==========================================
+ Coverage   72.39%   72.41%   +0.01%     
==========================================
  Files         133      133              
  Lines       40253    40281      +28     
  Branches    40253    40281      +28     
==========================================
+ Hits        29142    29169      +27     
  Misses       9240     9240              
- Partials     1871     1872       +1     

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