Fixes cartant#100

There's also a proposed fix PR in the upstream repo
cartant#114 but I avoided
looking at that solution to avoid any license issue, so this solution
might be different.

- Fix: if the `shareReplay` operator was passed an object config, then
require `bufferSize` to be in that object.
- Fix: the rule wasn't handling if `shareReplay` is imported under a
namespace.
- (Might need to review the entire project. Since rxjs now recommends
importing from "rxjs" instead of "rxjs/operators", there's a risk that
many rules also fail to account for that new paradigm. Note that this
rule is the only rule that tests namespace imports for all cases, so we
at least should expand that coverage/type of test.)