Extend merge url params to remove null values

What does this MR do?

Improvment part of #215473 (closed)

Extend merge url params to remove null values

When new parameters are added to a URL some of them may be null.

This change prevents actual result of string null and instead removes them so mergeUrlParams are more flexible.

Note: Handling undefined cases is out of scope for this MR, I consider this behavior should not be supported.

Screenshots

NA

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
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• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
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Security

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• Label as security and @ mention @gitlab-com/gl-security/appsec
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