SNOW-2752334: Fix overlap handling when parsing XML file

[sfc-gh-aalam]

1. Which Jira issue is this PR addressing? Make sure that there is an accompanying issue to your PR.

   Fixes SNOW-2752334

2. Fill out the following pre-review checklist:

   • I am adding a new automated test(s) to verify correctness of my new code
     • If this test skips Local Testing mode, I'm requesting review from @snowflakedb/local-testing
   • I am adding new logging messages
   • I am adding a new telemetry message
   • I am adding new credentials
   • I am adding a new dependency
   • If this is a new feature/behavior, I'm adding the Local Testing parity changes.
   • I acknowledge that I have ensured my changes to be thread-safe. Follow the link for more information: Thread-safe Developer Guidelines
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3. Please describe how your code solves the related issue.

   When parsing the XML file chunk by chunk to find the start pos of start of row tag, the code was loading the overlap into memory but also doing a file seek to undo the overlap causing invalid file parsing. This change removes the file seek line.

[sfc-gh-aalam]

this code is looking for start tag in the last chunk and raising EOF errors if tag is not found in chunk. This is not correct since code below start line 210, we look for tag in data = overlap + chunk. If in the last chunk, the start row tag was part of overlap, we will miss it and raise a false error.

[sfc-gh-aalam]

line 230 is already reading overlapped data into overlap. we don't need to seek back. The absolute_pos calculation on line 222 also accounts for this.

[sfc-gh-aalam]

These are flaky due to sort order. Making them unflaky.