Truncate waltmp file on creation

[petuhovskiy]

Previously in safekeeper code, new segment file was opened without truncate option. I don't think there is a reason to do it, this commit replaces it with File::create to make it simpler and remove clippy::suspicious_open_options linter warning.

[github-actions]

2916 tests run: 2799 passed, 0 failed, 117 skipped (full report)

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Code coverage* (full report)

• functions: 32.5% (6866 of 21131 functions)
• lines: 50.0% (53370 of 106768 lines)

* collected from Rust tests only

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_{The comment gets automatically updated with the latest test results
361d6f8 at 2024-06-24T13:34:07.633Z :recycle:}