Use src/ imports in addons; bundle test output via esbuild

Addons no longer import from out/ or out-esbuild in source. TypeScript
and editors resolve ../../../src/common|browser directly. Addon unit test
artifacts bundle those dependencies from source (platform node, npm
packages external).

Reverts preserveConstEnums; const enums are handled in bundled output.

Co-authored-by: Daniel Imms <Tyriar@users.noreply.github.com>

src/tsconfig-library-base.json

@@ -5,7 +5,6 @@
     "strict": true,
     "declarationMap": true,
     "experimentalDecorators": true,
-    "downlevelIteration": true,
-    "preserveConstEnums": true
+    "downlevelIteration": true
   }
 }