Small fix for column filtering

[Bastianciito]

Related Issues/PRs

What changes are proposed in this pull request?

In Databricks, vector columns that are automatically created when building a vector index typically follow a specific naming pattern, for example, a column named merged_text will produce a vector column named __db_merged_text_vector by default

Previously, the pattern used to filter out these vector columns was hardcoded and fixed, which could lead to conflicts for custom indexes that a user may create (I was one of them)

This PR changes that logic by introducing explicit constants for the prefix and suffix patterns used to identify these vector columns.

How is this PR tested?

• [ X] Existing unit/integration tests
• New unit/integration tests
• Manual tests

Does this PR require documentation update?

• [ X] No. You can skip the rest of this section.
• Yes. I've updated the relevant server README.md

Release Notes

Is this a user-facing change?

• [ x] No. You can skip the rest of this section.
• Yes. Give a description of this change to be included in the release notes.

How should the PR be classified in the release notes? Choose one:

• [x ] rn/none - No description will be included. The PR will be mentioned only by the PR number in the "Small Bugfixes and Documentation Updates" section
• rn/breaking-change - The PR will be mentioned in the "Breaking Changes" section
• rn/feature - A new user-facing feature worth mentioning in the release notes
• rn/bug-fix - A user-facing bug fix worth mentioning in the release notes
• rn/documentation - A user-facing documentation change worth mentioning in the release notes