Add stub for runtime numcgocall and numgoroutine

[attriaayush]

This adds a stub for NumCgoCall, NumGoroutine and Version functions from the runtime package.

Since the multi-threading is currently not supported, hard coding NumGoroutine value to 1 (main thread), NumCgoCall to 0 and lastly for the Version It is either the commit hash, date of the build or release tag but I have just put in v0.1.0 for now. From what I can see this change should not break anything since these functions don't already exist.

[dgryski]

Note that Version is also being discussed here: #2676

[attriaayush]

Note that Version is also being discussed here: #2676

@dgryski That makes sense, happy to remove the changes related to Version in that case from this PR.

[aykevl]

Since the multi-threading is currently not supported, hard coding NumGoroutine value to 1 (main thread)

TinyGo does support goroutines. So returning 1 is technically incorrect. But TinyGo doesn't currently track which goroutines are still alive (they just get garbage collected when finished) so there is no way to know.
But for compatibility, this might be fine.

NumCgoCall to 0

For compatibility, I think returning 0 would be fine.

Can you update the comments to point out these are stubs and don't return the real value?