bump TiDB Operator to 1.6.0 and TiDB to 8.1.0

[csuzhangxc]

What problem does this PR solve?

What is changed and how does it work?

Code changes

• [ ] Has Go code change
• [ ] Has CI related scripts change

Tests

• [ ] Unit test
• [ ] E2E test
• [ ] Manual test
• [ ] No code

Side effects

• [ ] Breaking backward compatibility
• [ ] Other side effects:

Related changes

• [ ] Need to cherry-pick to the release branch
• [ ] Need to update the documentation

Release Notes

Please refer to Release Notes Language Style Guide before writing the release note.

[ti-chi-bot[bot]]

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[csuzhangxc]

/run-all-tests

[codecov-commenter]

Codecov Report

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

Project coverage is 34.92%. Comparing base (3897095) to head (06ab524). Report is 9 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #5641 +/- ## =========================================== - Coverage 61.46% 34.92% -26.54% =========================================== Files 235 219 -16 Lines 30397 30425 +28 =========================================== - Hits 18683 10626 -8057 - Misses 9840 18410 +8570 + Partials 1874 1389 -485 ``` | [Flag](https://app.codecov.io/gh/pingcap/tidb-operator/pull/5641/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pingcap) | Coverage Δ | | |---|---|---| | [e2e](https://app.codecov.io/gh/pingcap/tidb-operator/pull/5641/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pingcap) | `34.92% <ø> (?)` | | | [unittest](https://app.codecov.io/gh/pingcap/tidb-operator/pull/5641/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pingcap) | `?` | |

[csuzhangxc]

/run-pull-e2e-kind

[csuzhangxc]

/run-pull-e2e-kind-basic

[csuzhangxc]

/run-pull-e2e-kind-across-kubernetes

[csuzhangxc]

/run-pull-e2e-kind-tikv-scale-simultaneously

[csuzhangxc]

/run-all-tests

[csuzhangxc]

/run-pull-e2e-kind

[csuzhangxc]

/run-pull-e2e-kind-across-kubernetes