(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/SearchModel.ts

@@ -84,7 +84,7 @@ export class SearchModelImpl extends Disposable implements SearchModel {
 
     // Listen to input value changes (debounced) to activate searching.
     const findFirst = debounce((_value: string) => this._findFirst(_value), 100);
-    this.autoDispose(this.value.addListener(v => { findFirst(v); }));
+    this.autoDispose(this.value.addListener(v => { void findFirst(v); }));
   }
 
   public async findNext() {