(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/components/ActionLog.ts

@@ -262,7 +262,7 @@ export class ActionLog extends dispose.Disposable implements IDomComponent {
     if (this._loaded || !this._gristDoc) { return; }
     this._loading(true);
     // Returned actions are ordered with earliest actions first.
-    const result = await this._gristDoc!.docComm.getActionSummaries();
+    const result = await this._gristDoc.docComm.getActionSummaries();
     this._loading(false);
     this._loaded = true;
     // Add the actions to our action log.