Remove TypeScript path mappings in favor of relative imports

Fixes https://github.com/xtermjs/xterm.js/issues/5896

TypeScript path mappings for common/*, browser/*, and headless/*
were not rewritten in emitted JavaScript, which forced webpack resolve
aliases and NODE_PATH workarounds so runtime could resolve modules.
That added build complexity and broke tooling such as ESLint import/no-cycle.

Changes:
- Convert ~750 imports across src/, addons/, and test/ to relative paths
- Remove common/browser/headless paths and src catch-all mappings from tsconfigs
  (keep @xterm/addon-* demo and addon typings paths)
- Remove webpack resolve.alias for common, browser, headless, and vs
- Drop NODE_PATH from unit tests, benchmarks, and VS Code launch config
- Fix addon-image IIPImageStorage to import ./Types after removing catch-all *

Verified: npm run build, esbuild, package, package-headless
Co-authored-by: Cursor <cursoragent@cursor.com>

src/common/input/UnicodeV6.ts

@@ -2,8 +2,8 @@
  * Copyright (c) 2019 The xterm.js authors. All rights reserved.
  * @license MIT
  */
-import { IUnicodeVersionProvider, UnicodeCharProperties, UnicodeCharWidth } from 'common/services/Services';
-import { UnicodeService } from 'common/services/UnicodeService';
+import { IUnicodeVersionProvider, UnicodeCharProperties, UnicodeCharWidth } from '../services/Services';
+import { UnicodeService } from '../services/UnicodeService';
 
 const BMP_COMBINING = [
   [0x0300, 0x036F], [0x0483, 0x0486], [0x0488, 0x0489],