Oracle Datasource: Inconsistent behavior between `$timeFilter`/`$timeFilterTZ` and `$timeGroup`/`$timeGroupTZ`

### What happened? There’s an inconsistency in how filter vs group macros handle timezone parameters: `$timeFilter` and `$timeFilterTZ` currently behave the same (both always use the datasource-configured timezone). - https://github.com/grafana/plugins-private/blob/86d2e4de58e074cd4657a208964f4313600ab077/plugins/grafana-oracle-datasource/pkg/oracle/macros.go#L103 - https://github.com/grafana/plugins-private/blob/86d2e4de58e074cd4657a208964f4313600ab077/plugins/grafana-oracle-datasource/pkg/oracle/macros.go#L108 `$timeGroup` and `$timeGroupTZ` differ. `$timeGroup` uses the datasource-configured timezone. `$timeGroupTZ` does not. - https://github.com/grafana/plugins-private/blob/86d2e4de58e074cd4657a208964f4313600ab077/plugins/grafana-oracle-datasource/pkg/oracle/macros.go#L122 - https://github.com/grafana/plugins-private/blob/86d2e4de58e074cd4657a208964f4313600ab077/plugins/grafana-oracle-datasource/pkg/oracle/macros.go#L128 This inconsistency makes it difficult for users to predict how macros behave. Queries using `$timeFilter/$timeFilterTZ` vs `$timeGroup/$timeGroupTZ` may produce inconsistent results when timezone-sensitive fields are involved. ### What did you expect to happen? Macro naming should be consistent and intuitive. Suggested behavior: `$timeFilter / $timeGroup` → always use UTC `$timeFilterTZ / $timeGroupTZ` → always use the datasource’s configured timezone Backwards compatibility should be considered to prevent breaking existing users. ### Did this work before? N/A ### How do we reproduce it? 1. Configure the Oracle datasource with a non-UTC timezone (e.g. America/New_York). 2. Run a query with a $timeFilter on a system table such as V$SESSION, which uses UTC columns. 3. `SELECT * FROM V$SESSION WHERE $timeFilter(LOGON_TIME)` 4. Observe that records are either missing or shifted in time because the filter applies the datasource timezone instead of UTC. 5. Change the datasource timezone to UTC and re-run the query. 6. Now the expected rows appear. ###…