fix: trim leading '/'s for files specified in copy opt

[dantengsky]

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Summary

This PR introduces a modification to the handling of file paths in COPY INTO table statements. Specifically, when using statements like (files are explicitly specified by copy-option files):

copy into t from  @ts file_format = (type = CSV) files =('///a.csv') purge = true force = false;

The leading slashes in the file path (e.g., ///a.csv) will now be trimmed before the file names are stored in the meta server (in this case a.csv). This change aligns with the behavior observed when using COPY INTO table statements that copy data from a location without specifying individual file names, such as:

copy into t from  @ts file_format = (type = CSV)  purge = true force = false;

With this update, the file names recorded in the meta server will be consistent across different COPY INTO usage patterns, ensuring uniformity when the same files are copied.

• Fixes bug: purge of copy-into not work as expected #15039

Tests

• Unit Test
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Type of change

• Bug Fix (non-breaking change which fixes an issue)
• New Feature (non-breaking change which adds functionality)
• Breaking Change (fix or feature that could cause existing functionality not to work as expected)
• Documentation Update
• Refactoring
• Performance Improvement
• Other (please describe):