QueryOptions: update maxDataPoints text and show any value that is configured (#18761)

* update maxDataPoints UI

* use maxDataPoints to calculate interval

* don't change interval calculation

public/app/plugins/datasource/testdata/StreamHandler.ts

@@ -175,9 +175,9 @@ export class SignalWorker extends StreamWorker {
   };
 
   initBuffer(refId: string) {
-    const { speed, buffer } = this.query;
+    const { speed } = this.query;
     const request = this.stream.request;
-    const maxRows = buffer ? buffer : request.maxDataPoints;
+    const maxRows = request.maxDataPoints || 1000;
     const times = new CircularVector({ capacity: maxRows });
     const vals = new CircularVector({ capacity: maxRows });
     this.values = [times, vals];
@@ -341,11 +341,11 @@ export class LogsWorker extends StreamWorker {
   };
 
   initBuffer(refId: string) {
-    const { speed, buffer } = this.query;
+    const { speed } = this.query;
 
     const request = this.stream.request;
 
-    const maxRows = buffer ? buffer : request.maxDataPoints;
+    const maxRows = request.maxDataPoints || 1000;
 
     const times = new CircularVector({ capacity: maxRows });
     const lines = new CircularVector({ capacity: maxRows });

public/app/plugins/datasource/testdata/plugin.json

@@ -9,7 +9,8 @@
   "annotations": true,
 
   "queryOptions": {
-    "minInterval": true
+    "minInterval": true,
+    "maxDataPoints": true
   },
 
   "info": {

public/app/plugins/datasource/testdata/types.ts

@@ -18,7 +18,6 @@ export interface StreamingQuery {
   speed: number;
   spread: number;
   noise: number; // wiggle around the signal for min/max
-  bands?: number; // number of bands around the middle van
-  buffer?: number;
+  bands?: number; // number of bands around the middle band
   url?: string; // the Fetch URL
 }