test: add 1mb.txt file to the object storage tests

What does this MR do?

1MB is enough to trigger multiple read (hence range requests since we are using an object storage).

The file was copied from https://gist.github.com/khaykov/a6105154becce4c0530da38e723c2330

A recent incident was caused by inconsistencies with subsequent reads, this is aimed to prevent such issues.

The previous test was not enough because the files are not big enough to trigger multiple reads. Additionally smaller files are not compressed.

See gitlab-com/gl-infra/production#7438 (closed)

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To verify the content mismatch issue:

• checkout this branch
• cherry-pick the lazy file commit: git cherry-pick 57195a5ae472878c19dae4b6a65bc37a76e992e4
• make test will fail

TODO

• I added the Changelog trailer (e.g. Changelog: added) to the commits that need to be included in the changelog
• I added unit tests or they are not required
• I added acceptance tests or they are not required
• I added documentation (or it's not required)
• I followed code review guidelines
• I followed Go Style guidelines