chore: add form_type parameter argument to db (#17920)

`form_type` is a new parameter field in the terraform provider. Bring
that field into coder/coder.

Validation for `multi-select` has also been added.

coderd/database/migrations/000333_parameter_form_type.down.sql

@@ -0,0 +1,2 @@
+ALTER TABLE template_version_parameters DROP COLUMN form_type;
+DROP TYPE parameter_form_type;

coderd/database/migrations/000333_parameter_form_type.up.sql

@@ -0,0 +1,11 @@
+CREATE TYPE parameter_form_type AS ENUM ('', 'error', 'radio', 'dropdown', 'input', 'textarea', 'slider', 'checkbox', 'switch', 'tag-select', 'multi-select');
+COMMENT ON TYPE parameter_form_type
+	IS 'Enum set should match the terraform provider set. This is defined as future form_types are not supported, and should be rejected. '
+	'Always include the empty string for using the default form type.';
+
+-- Intentionally leaving the default blank. The provisioner will not re-run any
+-- imports to backfill these values. Missing values just have to be handled.
+ALTER TABLE template_version_parameters ADD COLUMN form_type parameter_form_type NOT NULL DEFAULT '';
+
+COMMENT ON COLUMN template_version_parameters.form_type
+	IS 'Specify what form_type should be used to render the parameter in the UI. Unsupported values are rejected.';