Add Managing Agency filter functionality

[TylerMatteo]

Acceptance Criteria

• Add new "Search by Attribute" section on mobile and desktop (designs)
• Add managing agency dropdown, populated with /agencies endpoint.
• "Search" button is disabled until user selects an agency
• When user clicks "Search", projects on map and in list are filtered to only those belonging to the given agency. Query parameter for agency should be reflected in browser query params

Notes

• Do not include dropdown for Project Type or slider for Project Amount in this Issue - those will be added in separate Issues.
• Do not include "Reset Selection" clickable text - will be added in separate Issue
• Deck's DataFilterExtension should be helpful for filtering on the map.

[TangoYankee]

When user clicks "Search", projects on map and in list are filtered to only those belonging to the given agency. Query parameter for agency should be reflected in browser query params

And if the user has a geography selected, it should also apply that geography filter?