fix(runtime): Lookup into native MD tables when searching by name

[mbektchiev]

Querying metadata for Objective-C interfaces and protocols should not be done by the JS name when the string we search for is actually their native name

• Introduce 2 additional global tables in metadata for Interfaces and Protocols indexed by their native name
• Make Metadata::GlobalTable a template struct and move its implementation to MetadataInlines.h
• Use the correct global table depending on the name and entity being looked up
• Add unit test with an objc_runtime_name attribute emulating that it's been generated by the Swift compiler

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
• [x] Tests for the changes are included.

refs #712