(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/common/PluginInstance.ts

@@ -76,7 +76,7 @@ export abstract class BaseComponent implements IForwarderDest {
   public async forwardMessage(msg: IMsgCustom): Promise<any> {
     if (!this._activated) { await this.activate(); }
     this.inactivityTimer.ping();
-    this.doForwardMessage(msg); // tslint:disable-line:no-floating-promises TODO
+    this.doForwardMessage(msg); // eslint-disable-line @typescript-eslint/no-floating-promises
   }
 
   protected abstract doForwardCall(c: IMsgRpcCall): Promise<any>;