tiup: add 4 docs dm-edit config/help/scale in/scale out

[Joyinqin]

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)

Add 4 docs:

• tiup/tiup-component-dm-edit-config.md
• tiup/tiup-component-dm-help.md
• tiup/tiup-component-dm-scale-in.md
• tiup/tiup-component-dm-scale-out.md

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

• master (the latest development version)
• v5.0 (TiDB 5.0 versions)
• v4.0 (TiDB 4.0 versions)
• v3.1 (TiDB 3.1 versions)
• v3.0 (TiDB 3.0 versions)
• v2.1 (TiDB 2.1 versions)

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

• This PR is translated from: tiup: refactor tiup reference docs-cn#4868
• 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

[lucklove]

/lgtm

[ran-huang]

Rest LGTM

[Joyinqin]

/sig tiup

[Joyinqin]

/sig docs

[ran-huang]

/lgtm

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• lucklove
• ran-huang

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[ran-huang]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: 13fcbe2

[ti-srebot]

cherry pick to release-4.0 in PR #5332

[ti-srebot]

cherry pick to release-5.0 in PR #5333