fix per folder provide browse configuration

[gcampbell-msft]

We were returning the most recent stored browse configuration, which may be incorrect. Rather, we should return null if we don't have the browseConfiguration for the requested URI.

This change addresses item [#3155]

This changes the implementation of provideFolderBrowseConfiguration

The following changes are proposed:

• Return null instead of a default / last stored workspaceBrowseConfiguration

The purpose of this change

We were returning what effectively was the default or last stored workspaceBrowseConfiguration if we didn't have stored a browseConfiguration for that URI. This is incorrect as that default or last stored has no guarantee of actually applying. We instead return null.

Closes #3155

[sean-mcmanus]

I don't understand the code base, but if it fixes the bug then that sounds good to me. I assume you got a repro from Colen.

[snehara99]

I don't think the checks like that the return could be null. Does this check need to be bypassed or is there another option?

[gcampbell-msft]

I don't think the checks like that the return could be null. Does this check need to be bypassed or is there another option?

@snehara99 THis has been fixed, ping for review. Thanks!