(core) Configure more comprehensive eslint rules for Typescript

Summary:
- Update rules to be more like we've had with tslint
- Switch tsserver plugin to eslint (tsserver makes for a much faster way to lint in editors)
- Apply suggested auto-fixes
- Fix all lint errors and warnings in core/, app/, test/

Test Plan: Some behavior may change subtly (e.g. added missing awaits), relying on existing tests to catch problems.

Reviewers: paulfitz

Reviewed By: paulfitz

Differential Revision: https://phab.getgrist.com/D2785

app/client/models/DocData.ts

@@ -100,7 +100,7 @@ export class DocData extends BaseDocData {
         this._nextDesc = options.description;
         this._lastActionNum = null;
         this._triggerBundleFinalize = triggerFinalize;
-        await prepareResolve(options.prepare());
+        prepareResolve(options.prepare());
         this._shouldIncludeInBundle = options.shouldIncludeInBundle;
 
         await triggerFinalizePromise;
@@ -162,7 +162,7 @@ export class DocData extends BaseDocData {
   public sendActions(actions: UserAction[], optDesc?: string): Promise<any[]> {
     // Some old code relies on this promise being a bluebird Promise.
     // TODO Remove bluebird and this cast.
-    return bluebird.Promise.resolve(this._sendActionsImpl(actions, optDesc)) as any;
+    return bluebird.Promise.resolve(this._sendActionsImpl(actions, optDesc)) as unknown as Promise<any[]>;
   }
 
   /**