fix: correctly recognize existing delta tables using the transaction log

[stretchadito]

Description

In logstore.is_delta_table_location(), if a checkpoint file is the earliest/first file in a table's transaction log, the table should be positively identified as a delta table. (Currently, it only recognizes delta tables for which a commit json is the first file in the transaction log)

Related Issue(s)

• Closes Log store may erroneously consider valid delta tables to be nonexistent #3004

[codecov]

Codecov Report

Attention: Patch coverage is 89.83051% with 6 lines in your changes missing coverage. Please review.

Project coverage is 72.41%. Comparing base (d4f18b3) to head (10d686d).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/core/src/logstore/mod.rs	89.83%	0 Missing and 6 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3005      +/-   ##
==========================================
+ Coverage   72.35%   72.41%   +0.05%     
==========================================
  Files         128      128              
  Lines       40467    40525      +58     
  Branches    40467    40525      +58     
==========================================
+ Hits        29281    29346      +65     
+ Misses       9308     9303       -5     
+ Partials     1878     1876       -2     

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