Non ascii character support

[josstn]

This replaces regexp patterns that only worked with ascii characters with more proper matching that supports unicode identifiers in typescript/javascript.

So that the generated code can have valid unicode characters in enum, type, service, operation and parameter names.

The platform must support "unicode-aware mode" (the u flag) for this to work. https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp/unicode

This PR replaces #2038