Respect timezone in QAN

In scope of https://jira.percona.com/browse/PMM-9775 UTC was fixed, but it needs to be properly fixed to handle any other timezone and without workarounds.

AC:

1: FE should send datetime with timezone as it was selected by the user.

2: BE should return result for the same timezone.

3: Cleanup FE for utc conversion, in general utc should not be used, instead we should use datetime with timezone.

Align progress with