(core) Speed up and upgrade build.

Summary:
- Upgrades to build-related packages:
  - Upgrade typescript, related libraries and typings.
  - Upgrade webpack, eslint; add tsc-watch, node-dev, eslint_d.

- Build organization changes:
  - Build webpack from original typescript, transpiling only; with errors still
    reported by a background tsc watching process.

- Typescript-related changes:
  - Reduce imports of AWS dependencies (very noticeable speedup)
  - Avoid auto-loading global @types
  - Client code is now built with isolatedModules flag (for safe transpilation)
  - Use allowJs to avoid copying JS files manually.

- Linting changes
  - Enhance Arcanist ESLintLinter to run before/after commands, and set up to use eslint_d
  - Update eslint config, and include .eslintignore to avoid linting generated files.
  - Include a bunch of eslint-prompted and eslint-generated fixes
  - Add no-unused-expression rule to eslint, and fix a few warnings about it

- Other items:
  - Refactor cssInput to avoid circular dependency
  - Remove a bit of unused code, libraries, dependencies

Test Plan: No behavior changes, all existing tests pass. There are 30 tests fewer reported because `test_gpath.py` was removed (it's been unused for years)

Reviewers: paulfitz

Reviewed By: paulfitz

Subscribers: paulfitz

Differential Revision: https://phab.getgrist.com/D3498

app/common/DocActions.ts

@@ -4,7 +4,7 @@
 
 // Some definitions have moved to be part of plugin API.
 import { BulkColValues, CellValue, RowRecord } from 'app/plugin/GristData';
-export { BulkColValues, CellValue, RowRecord } from 'app/plugin/GristData';
+export type { BulkColValues, CellValue, RowRecord };
 
 // Part of a special CellValue used for comparisons, embedding several versions of a CellValue.
 export interface AllCellVersions {
@@ -173,7 +173,7 @@ export function getNumRows(action: DocAction): number {
 export function toTableDataAction(tableId: string, colValues: TableColValues): TableDataAction {
   const colData = {...colValues};   // Make a copy to avoid changing passed-in arguments.
   const rowIds: number[] = colData.id;
-  delete colData.id;
+  delete (colData as BulkColValues).id;
   return ['TableData', tableId, rowIds, colData];
 }