Add "Other waterbody" button to Waterbody dropdown to more easily add manual entries

[davidclaveau]

Describe the task Allow the user to add a waterbody manually by selecting "other waterbodies" in the waterbody dropdown.

Purpose Give a clear and efficient workflow for the user to add a waterbody manually. Instead of them typing "other" in the search - and finding the hidden manual entry UI that appears - they can search for "other" naturally and get the manual entry UI.

Acceptance Criteria

• [x] "Other waterbody" should appear in the dropdown
• [x] When selecting "Other waterbody", the manual entry UI should appear for the user

Additional context

[davidclaveau]

Added an "Other waterbody not listed" button at the bottom of the Waterbody picker that will call the same functionality as typing "other" in the search function. This will open the UI to add a waterbody manually.