fix: Use Map for O(1) column lookups in table width calculations

[TrevorBurnham]

Description

Currently the table width calculations use repeated find calls across columns in getColumnStyles, which is called for each column, so worst-case performance is O(n^2). This PR switches to creating a Map for that lookup, making performance consistently O(n).

How has this been tested?

This functionality is well-covered by existing tests.

Review checklist

The following items are to be evaluated by the author(s) and the reviewer(s).

Correctness

• Changes include appropriate documentation updates.
• Changes are backward-compatible if not indicated, see CONTRIBUTING.md.
• Changes do not include unsupported browser features, see CONTRIBUTING.md.
• Changes were manually tested for accessibility, see accessibility guidelines.

Security

• If the code handles URLs: all URLs are validated through the checkSafeUrl function.

Testing

• Changes are covered with new/existing unit tests?
• Changes are covered with new/existing integration tests?

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