fix: innerFrom throw ObservableTypeError when Observable Class is different (different version, duplicate code)

[MeetzhDing]

When using webpack or rollup, we may bundle different version rxjs into websites.

Function using innerFrom (eg. mergeMap, from) will throw InvalidObservableTypeError when input is not instanceOf current version Observable, and this problem is to hard to locate.

The util isObservable can solve this problem.

@benlesh

[MeetzhDing]

@benlesh please have a look at this pr.

[tien]

Same issue is happening with bundler like Vite