refactor(HMR): print caught error's message

[vchimev]

Print caught error's message on a module.hot.check() or a module.hot.apply() failure.

Also:

• expose a latestHash variable in the hmr-update.js,
• format properly the HMR_HANDLER snippet in bundles
• add module context parameter default value
• update module hot accept callback

PR Checklist

• The PR title follows our guidelines: https://github.com/NativeScript/NativeScript/blob/master/CONTRIBUTING.md#commit-messages.
• There is an issue for the bug/feature this PR is for. To avoid wasting your time, it's best to open a suggestion issue first and wait for approval before working on it.
• You have signed the CLA.
• All existing tests are passing: https://github.com/NativeScript/nativescript-dev-webpack/blob/master/CONTRIBUTING.md#testing-locally-by-running-e2e-tests
• Tests for the changes are included.

What is the current behavior?

Currently, if module.hot.check() or module.hot.apply() throws an error, the error's trace is printed.

What is the new behavior?

Print error's message if truthy, if not - print error's trace.

[sis0k0]

Even better - print both.

[vchimev]

I don't think it's needed - messages look descriptive enough, i.e.:

CONSOLE INFO file:///app/vendor.js:72111:36: HMR: Checking for updates to the bundle with hmr hash 1a369033d922096d2138.
CONSOLE WARN file:///app/vendor.js:72112:36: HMR: Ignored an update to unaccepted module:
CONSOLE WARN file:///app/vendor.js:72112:36: HMR:          ➭ ./main.ts
CONSOLE ERROR file:///app/vendor.js:72113:38: HMR: Cannot apply update with hmr hash 1a369033d922096d2138.
CONSOLE ERROR file:///app/vendor.js:72113:38: HMR: Aborted because ./main.ts is not accepted
Update propagation: ./main.ts

[sis0k0]

If you say so.