fix: disallow deselecting dynamic dropdown value (#22931)

This was accomplished by switching from the comboxbox (which has
deselection logic) to a select (which does not).

As a side effect, the dropdowns are wider now, which seems to match
better with other inputs anyway.  And, it seems it uses the `combobox`
role instead of `button` which also seems to make more sense.  Lastly, 
they lose some bolding.

site/src/modules/workspaces/DynamicParameter/DynamicParameter.jest.tsx

@@ -191,7 +191,7 @@ describe("DynamicParameter", () => {
 				/>,
 			);
 
-			const select = screen.getByRole("button");
+			const select = screen.getByRole("combobox");
 			await waitFor(async () => {
 				await userEvent.click(select);
 			});
@@ -211,7 +211,7 @@ describe("DynamicParameter", () => {
 				/>,
 			);
 
-			const select = screen.getByRole("button");
+			const select = screen.getByRole("combobox");
 			await waitFor(async () => {
 				await userEvent.click(select);
 			});
@@ -703,7 +703,7 @@ describe("DynamicParameter", () => {
 				/>,
 			);
 
-			expect(screen.getByRole("button")).toBeInTheDocument();
+			expect(screen.getByRole("combobox")).toBeInTheDocument();
 		});
 
 		it("handles null/undefined values", () => {

site/src/modules/workspaces/DynamicParameter/DynamicParameter.tsx

@@ -7,14 +7,6 @@ import type {
 import { Badge } from "components/Badge/Badge";
 import { Button } from "components/Button/Button";
 import { Checkbox } from "components/Checkbox/Checkbox";
-import {
-	Combobox,
-	ComboboxButton,
-	ComboboxContent,
-	ComboboxItem,
-	ComboboxList,
-	ComboboxTrigger,
-} from "components/Combobox/Combobox";
 import { ExternalImage } from "components/ExternalImage/ExternalImage";
 import { Input } from "components/Input/Input";
 import { Label } from "components/Label/Label";
@@ -24,6 +16,13 @@ import {
 	type Option,
 } from "components/MultiSelectCombobox/MultiSelectCombobox";
 import { RadioGroup, RadioGroupItem } from "components/RadioGroup/RadioGroup";
+import {
+	Select,
+	SelectContent,
+	SelectItem,
+	SelectTrigger,
+	SelectValue,
+} from "components/Select/Select";
 import { Slider } from "components/Slider/Slider";
 import { Stack } from "components/Stack/Stack";
 import { Switch } from "components/Switch/Switch";
@@ -335,41 +334,25 @@ const ParameterField: FC<ParameterFieldProps> = ({
 		}
 
 		case "dropdown": {
-			const selectedOption = parameter.options.find(
-				(opt) => opt.value.value === value,
-			);
 			return (
-				<Combobox
+				<Select
 					value={value}
 					onValueChange={(newValue) => onChange(newValue ?? "")}
+					disabled={disabled}
 				>
-					<ComboboxTrigger asChild>
-						<ComboboxButton
-							selectedOption={
-								selectedOption
-									? {
-											label: selectedOption.name,
-											value: selectedOption.value.value,
-										}
-									: undefined
-							}
+					<SelectTrigger>
+						<SelectValue
 							placeholder={parameter.styling?.placeholder || "Select option"}
-							disabled={disabled}
 						/>
-					</ComboboxTrigger>
-					<ComboboxContent>
-						<ComboboxList>
-							{parameter.options.map((option) => (
-								<ComboboxItem
-									key={option.value.value}
-									value={option.value.value}
-								>
-									{option.name}
-								</ComboboxItem>
-							))}
-						</ComboboxList>
-					</ComboboxContent>
-				</Combobox>
+					</SelectTrigger>
+					<SelectContent>
+						{parameter.options.map((option) => (
+							<SelectItem key={option.value.value} value={option.value.value}>
+								{option.name}
+							</SelectItem>
+						))}
+					</SelectContent>
+				</Select>
 			);
 		}
 

site/src/pages/CreateWorkspacePage/CreateWorkspacePage.jest.tsx

@@ -140,7 +140,8 @@ describe("CreateWorkspacePage", () => {
 			const instanceTypeField = screen.getByTestId(
 				"parameter-field-instance_type",
 			);
-			const instanceTypeSelect = within(instanceTypeField).getByRole("button");
+			const instanceTypeSelect =
+				within(instanceTypeField).getByRole("combobox");
 			expect(instanceTypeSelect).toBeInTheDocument();
 
 			jest.useFakeTimers();