Fix new filtered search with assignee wild card values None and Any

What does this MR do and why?

Adds the ability to filter assignees by None and Any in new GlFilteredSearch project/group issue boards.

Repro

• rails c
• Feature.enable(:issue_boards_filtered_search)
• Go to a project or group issue boards
• Filter by assigned "None" or "Any"

Result: You should see the board updated correctly AND the URL param contain assigne_wildcard_id

Describe in detail what your merge request does and why.

Resolves #349569 (closed)

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How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

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