faq: Describe in what condition TiDB and RawKV can be used together

[pingyu]

First-time contributors' checklist

• I've signed Contributor License Agreement that's required for repo owners to accept my contribution.

What is changed, added or deleted? (Required)

Describe in what condition TiDB & RawKV can be used together.

Since v6.1.0 TiDB & RawKV can be used together if API V2 is enabled:

Data is scoped according to different usage and API V2 supports co-existence of TiDB, Transactional KV, and RawKV applications in a single cluster.

But the relevant FAQ has not been changed accordingly yet.

Which TiDB version(s) do your changes apply to? (Required)

Tips for choosing the affected version(s):

By default, CHOOSE MASTER ONLY so your changes will be applied to the next TiDB major or minor releases. If your PR involves a product feature behavior change or a compatibility change, CHOOSE THE AFFECTED RELEASE BRANCH(ES) AND MASTER.

For details, see tips for choosing the affected versions.

• master (the latest development version)
• v8.2 (TiDB 8.2 versions)
• v8.1 (TiDB 8.1 versions)
• v8.0 (TiDB 8.0 versions)
• v7.6 (TiDB 7.6 versions)
• v7.5 (TiDB 7.5 versions)
• v7.1 (TiDB 7.1 versions)
• v6.5 (TiDB 6.5 versions)
• v6.1 (TiDB 6.1 versions)
• v5.4 (TiDB 5.4 versions)
• v5.3 (TiDB 5.3 versions)
• v5.2 (TiDB 5.2 versions)
• v5.1 (TiDB 5.1 versions)

What is the related PR or file link(s)?

• This PR is translated from:
• Other reference link(s):

Do your changes match any of the following descriptions?

• Delete files
• Change aliases
• Need modification after applied to another branch
• Might cause conflicts after applied to another branch

[pingyu]

@qiancai Comment addressed, PTAL~

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-06-07 08:39:50.142730518 +0000 UTC m=+108344.196042443: ☑️ agreed by dveeden.
• 2024-06-11 05:34:13.617589152 +0000 UTC m=+442807.670901076: ☑️ agreed by qiancai.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.6: #17846.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-8.0: #17847.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-8.1: #17848.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-6.1: #17849.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-6.5: #17850.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.1: #17851.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.5: #17852.