fix(api): apply filename query to recording download, do not clobber instance selector query param (backport #1937)

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Related to cryostatio/cryostat#1171
Depends on cryostatio/cryostat#1171

Description of the change:

Applies the same filename query parameter handling so that the backend sets the Content-Disposition header accordingly.

More importantly, updates the filename query parameter handling so not always hardcode the ? query string separator, and to only infix it if needed. Otherwise, when the Cryostat UI is running within an OpenShift Console Plugin context, the query string construction may conflict with the console proxy instance selector query string construction.

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This is an automatic backport of pull request #1937 done by [Mergify](https://mergify.com).

[github-actions]

This PR/issue depends on:

• fix(diagnostics): presigned download content type and filename handling cryostat#1171
  By Dependent Issues (🤖). Happy coding!

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