charts: add timezone support

[weekface]

What problem does this PR solve?

This PR adds timezone support for all charts, closes: #1123

For the tidb-cluster chart, we already have the timezone option(default UTC). If the user does not change it to a different value(for example: Aisa/Shanghai), all pods will not be recreated.
If the user changes it to other value(for example: Aisa/Shanghai), all the related pods (add a TZ env) will be recreated(rolling update).

Regard other charts, we don't have a timezone option in their values.yaml. We add the timezone option in this PR. Whether the user uses the old values.yaml or the new values.yaml, all the related pods (add a TZ env) will not be recreated(rolling update).

The related pods include pump, drainer, dicovery, monitor, scheduled backup, tidb-initializer, tikv-importer.

All images' time zone maintained by tidb-operator are UTC. You need to make sure that the time zone inside your images are UTC if you use your own images.

What is changed and how does it work?

Check List

Tests

• Manual test (add detailed scripts or steps below)
• No code

Code changes

• Has Helm charts change

Side effects

Related changes

• Need to cherry-pick to the release branch

Does this PR introduce a user-facing change?:

ACTION REQUIRED: 

This PR adds `timezone` support for [all charts](https://github.com/pingcap/tidb-operator/tree/master/charts).

For the `tidb-cluster` chart, we already have the `timezone` option(default `UTC`). If the user does not change it to a different value(for example: `Aisa/Shanghai`), all pods will not be recreated.
If the user changes it to other value(for example: `Aisa/Shanghai`), all the related pods (add a `TZ` env) will be recreated(rolling update).

Regard other charts, we don't have a `timezone` option in their `values.yaml`. We add the `timezone` option in this PR. Whether the user uses the old `values.yaml` or the new `values.yaml`, all the related pods (add a `TZ` env) will not be recreated(rolling update).

The related pods include `pump`, `drainer`, `dicovery`, `monitor`, `scheduled backup`, `tidb-initializer`, `tikv-importer`.

All images' time zone maintained by `tidb-operator` are `UTC`. You need to make sure that the time zone inside your images are `UTC` if you use your own images.

[weekface]

/run-e2e-in-kind

[weekface]

/run-e2e-in-kind

[onlymellb]

LGTM

[DanielZhangQD]

LGTM

[sre-bot]

cherry pick to release-1.0 failed