Fix(mergeUrlparams): handle arrays gracefully

What does this MR do?

This MR adds an option parameter to mergeUrlParams to spread array values into separate URL parameters.

Array parameters would before be combined into a single string rather than individual sets of key/value-pairs, which is necessary in some situations.

This will be used in this MR to handle url-sync'ing from nested components.

Screenshots

spreadArrays=false	spreadArrays=true

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• Separation of EE specific content

Availability and Testing

This adds an option that will be used in a successive MR and other usages that need this behavior on an opt-in basis and will be unchanged otherwise. This MR, therefore, comes with very little risk.

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• [-] Label as security and @ mention @gitlab-com/gl-security/appsec
• [-] The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• [-] Security reports checked/validated by a reviewer from the AppSec team

Related to #232465 (closed)

Related to !39603 (merged)