Explore: Clear errors after running a new query

[ivanahuckova]

Issue:
Any query error creates the red box. Changing and re-submitting query does not clear the error nor does it indicate a query was submitted, only if the follow up comes back with a 200 does it clear the error. +cc @slim-bean

What this PR does / why we need it:
This PR fixes the issue on 2 levels:

• It clears the red box if the queryResponse.state changes from Error to Loading, so we don't have to wait for the new queryResponse.
• When processing query response, we don't assume that loading was finished, but rely on actual loading state.

Before:

After:

Fixes:
#29242

[ivanahuckova]

@davkal @aocenas Is there a reason why we were setting loading state to false in processQueryResponse and not to value based on LoadingState?

[zoltanbedi]

Probably fixes #29242 as well

[aocenas]

Looks good, I assume the reason was that we did not have the sates specified the same way as now, back then. For example I think we did not do partial responses at the time so when you got response we assumed it was the end of it.