Annotate module wrapper functions in debug builds

[evanw]

Sometimes esbuild needs to wrap certain modules in a function when bundling. This is done both for lazy evaluation and for CommonJS modules that use a top-level return statement. Previously these functions were all anonymous, so stack traces for errors thrown during initialization looked like this:

Error: Electron failed to install correctly, please delete node_modules/electron and try installing again
    at getElectronPath (out.js:16:13)
    at out.js:19:21
    at out.js:1:45
    at out.js:24:3
    at out.js:1:45
    at out.js:29:3
    at out.js:1:45
    at Object.<anonymous> (out.js:33:1)

This release adds names to these anonymous functions when minification is disabled. The above stack trace now looks like this:

Error: Electron failed to install correctly, please delete node_modules/electron and try installing again
    at getElectronPath (out.js:19:15)
    at node_modules/electron/index.js (out.js:22:23)
    at __require (out.js:2:44)
    at src/base/window.js (out.js:29:5)
    at __require (out.js:2:44)
    at src/base/kiosk.js (out.js:36:5)
    at __require (out.js:2:44)
    at Object.<anonymous> (out.js:41:1)

This is similar to Webpack's development-mode behavior:

Error: Electron failed to install correctly, please delete node_modules/electron and try installing again
    at getElectronPath (out.js:23:11)
    at Object../node_modules/electron/index.js (out.js:27:18)
    at __webpack_require__ (out.js:96:41)
    at Object../src/base/window.js (out.js:49:1)
    at __webpack_require__ (out.js:96:41)
    at Object../src/base/kiosk.js (out.js:38:1)
    at __webpack_require__ (out.js:96:41)
    at out.js:109:1
    at out.js:111:3
    at Object.<anonymous> (out.js:113:12)

These descriptive function names will additionally be available when using a profiler such as the one included in the "Performance" tab in Chrome Developer Tools. Previously all functions were named (anonymous) which made it difficult to investigate performance issues during bundle initialization.

Closes #1236