Simplify profile selection UI (#1593)

## Changes

And recommend OAuth profiles for new users (who don't have pre-existing
profiles defined).

There are three main improvements:
- Remove confusing `(user to machine)` suffix for OAuth profile type
- Add `(recommended)` suffix to OAuth profile type (but only if there
are no pre-existing profiles)
- Remove separators with headings (make them headless). We already give
the context in the item descriptions, additional headings only create
clutter (and can even be confused, since they show up for the first item
in the group, instead of on top of the group)


New UI when there are no pre-existing profiles:


<img width="605" alt="Screenshot 2025-03-05 at 13 45 02"
src="https://github.com/user-attachments/assets/f3114a22-b5c3-4afa-ab1d-f78db9d11f5a"
/>

New UI when there are pre-existing profiles (we don't show `recommended`
for OAuth then):


<img width="606" alt="Screenshot 2025-03-05 at 13 44 03"
src="https://github.com/user-attachments/assets/484ea8d1-d608-4fc7-8fc3-d820523a0937"
/>



Old UI:


<img width="605" alt="Screenshot 2025-03-05 at 13 48 20"
src="https://github.com/user-attachments/assets/cc87af6e-9d83-4d4b-9249-8abe02853d61"
/>

<img width="605" alt="Screenshot 2025-03-05 at 13 47 47"
src="https://github.com/user-attachments/assets/1d04288b-2784-41fa-b46e-2d1b2e155934"
/>


## Tests

<!-- How is this tested? -->

Author: ilia-db

packages/databricks-vscode/src/configuration/LoginWizard.ts

@@ -134,19 +134,17 @@ export class LoginWizard {
     }
 
     private async getProfileQuickPickItems() {
-        const items: Array<AuthTypeQuickPickItem> = [];
-
         const profiles = (await this.getProfiles())
             .filter((profile) => {
                 return profile.host?.hostname === this.state.host!.hostname;
             })
             .map((profile) => {
                 const humanisedAuthType = humaniseSdkAuthType(profile.authType);
                 const detail = humanisedAuthType
-                    ? `Authenticate using ${humaniseSdkAuthType(
+                    ? `Select existing profile and authenticate using ${humaniseSdkAuthType(
                           profile.authType
                       )}`
-                    : `Authenticate using profile ${profile.name}`;
+                    : `Select existing profile and authenticate`;
 
                 return {
                     label: profile.name,
@@ -155,28 +153,20 @@ export class LoginWizard {
                     profile: profile.name,
                 };
             });
-
-        if (profiles.length !== 0) {
-            items.push(
-                {
-                    label: "Existing Databricks CLI Profiles",
-                    kind: QuickPickItemKind.Separator,
-                },
-                ...profiles
-            );
-        }
-        return items;
+        return profiles;
     }
+
     private async selectAuthMethod(
         input: MultiStepInput
     ): Promise<InputStep | void> {
         const items: Array<AuthTypeQuickPickItem> = [];
-        items.push(...(await this.getProfileQuickPickItems()));
+        const profileItems = await this.getProfileQuickPickItems();
+        items.push(...profileItems);
 
         const availableAuthMethods = authMethodsForHostname(this.state.host!);
-        if (availableAuthMethods.length !== 0) {
+        if (availableAuthMethods.length !== 0 && profileItems.length !== 0) {
             items.push({
-                label: "Create New Databricks CLI Profile",
+                label: "",
                 kind: QuickPickItemKind.Separator,
             });
         }
@@ -201,7 +191,9 @@ export class LoginWizard {
 
                 case "databricks-cli":
                     items.push({
-                        label: "OAuth (user to machine)",
+                        label:
+                            "OAuth" +
+                            (profileItems.length === 0 ? " (recommended)" : ""),
                         detail: "Create a profile and authenticate using OAuth",
                         authType: "databricks-cli",
                     });
@@ -439,9 +431,9 @@ function humaniseSdkAuthType(sdkAuthType: string) {
         case "google-id":
             return "Google Service Account";
         case "databricks-cli":
-            return "OAuth (User to Machine)";
+            return "OAuth";
         case "oauth-m2m":
-            return "OAuth (Machine to Machine)";
+            return "OAuth M2M (Machine to Machine)";
         default:
             return sdkAuthType;
     }