refactor(debugging): Chrome DevTools Runtime domain logic

[mbektchiev]

Move the logic from core modules to iOS runtime. This way watches and expressions evaluation in console will work for apps which do not use the core modules (e.g. TestRunner of iOS runtime):

• Send executionContextCreated event when PageAgent is enabled
• Add dummy implementation for Runtime.compileScript message

PR Checklist

• [x] The PR title follows our guidelines: https://github.com/NativeScript/NativeScript/blob/master/CONTRIBUTING.md#commit-messages.
• [x] 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.
• [x] You have signed the CLA.
• [x] All existing tests are passing: https://github.com/NativeScript/ios-runtime/blob/master/CONTRIBUTING.md#contribute-to-the-code-base
• [ ] Tests for the changes are included.

refs #905 Merge along with https://github.com/NativeScript/NativeScript/pull/8072