Split runtime/lib/byte_array.dart into interfaces and (VM) implementation

[rakudrama]

This is a prerequisite for any work on unifying JavaScript typed arrays with the Dart typed arrays.

The interfaces need to be moved somewhere shared (core?)
Interfaces should be documented first.

[rakudrama]

Removed Type-Defect label.
Added Type-Enhancement label.

[vsmenon]

Marked this as blocking #3615.

[iposva-google]

Set owner to @sgmitrovic.

Added this to the M1 milestone.
Marked this as being blocked by #1499.
Unmarked this as being blocked by #1499.

Set owner to @iposva-google.

[iposva-google]

Removed this from the M1 milestone.
Added this to the M2 milestone.

[lexprfuncall]

I believe this issue has been fixed, at least to the extent that it no longer needs to be a blocking issue for other issues, notably

https://code.google.com/p/dart/issues/detail?id=3615

If there is still work to do we can re-open this issue.

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Added Fixed label.