Add empty tree state for SQL sidebar

Description

Issues Resolved

fixes empty state in side tree for opensearch and s3 datasource
Copy update for text in loading and empty state
Stops polling on cancel query

Check List

[ ] New functionality includes testing.
- [ ] All tests pass, including unit test, integration test and doctest
[ ] New functionality has been documented.
- [ ] New functionality has javadoc added
- [ ] New functionality has user manual doc added
[x] Commits are signed per the DCO using --signoff

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Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 59.29%. Comparing base (d168db7) to head (e941606).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #292 +/- ## ========================================== - Coverage 59.34% 59.29% -0.06% ========================================== Files 39 39 Lines 1835 1840 +5 Branches 328 330 +2 ========================================== + Hits 1089 1091 +2 - Misses 633 636 +3 Partials 113 113 ``` | [Flag](https://app.codecov.io/gh/opensearch-project/dashboards-query-workbench/pull/292/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=opensearch-project) | Coverage Δ | | |---|---|---| | [dashboards-query-workbench](https://app.codecov.io/gh/opensearch-project/dashboards-query-workbench/pull/292/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=opensearch-project) | `59.29% <ø> (-0.06%)` | :arrow_down: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=opensearch-project#carryforward-flags-in-the-pull-request-comment) to find out more.

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opensearch-project / dashboards-query-workbench