(core) Add Support Grist page and nudge

Summary:
Adds a new Support Grist page (accessible only in grist-core), containing
options to opt in to telemetry and sponsor Grist Labs on GitHub.

A nudge is also shown in the doc menu, which can be collapsed or permanently
dismissed.

Test Plan: Browser and server tests.

Reviewers: paulfitz, dsagal

Reviewed By: paulfitz

Subscribers: jarek, dsagal

Differential Revision: https://phab.getgrist.com/D3926

app/server/lib/sendAppPage.ts

@@ -76,7 +76,7 @@ export function makeGristConfig(options: MakeGristConfigOptons): GristLoadConfig
     featureFormulaAssistant: isAffirmative(process.env.GRIST_FORMULA_ASSISTANT),
     supportEmail: SUPPORT_EMAIL,
     userLocale: (req as RequestWithLogin | undefined)?.user?.options?.locale,
-    telemetry: server ? getTelemetryConfig(server) : undefined,
+    telemetry: server?.getTelemetry().getTelemetryConfig(),
     deploymentType: server?.getDeploymentType(),
     ...extra,
   };
@@ -163,13 +163,6 @@ function getFeatures(): IFeature[] {
   return Features.checkAll(difference(enabledFeatures, disabledFeatures));
 }
 
-function getTelemetryConfig(server: GristServer) {
-  const telemetry = server.getTelemetry();
-  return {
-    telemetryLevel: telemetry.getTelemetryLevel(),
-  };
-}
-
 function configuredPageTitleSuffix() {
   const result = process.env.GRIST_PAGE_TITLE_SUFFIX;
   return result === "_blank" ? "" : result;