cdc: reformat Changefeed config and Server config (#19166)

[ti-chi-bot]

This is an automated cherry-pick of #19166

What is changed, added or deleted? (Required)

This PR is a first step. It converts the existing format of code blocks to the body heading format for config descriptions in CLI and Configuration Parameters of TiCDC Changefeeds | TiDB Docs and TiCDC Server Configurations | TiDB Docs, like that in TiDB Configuration File | TiDB Docs.

This PR doesn't add new descriptions, except describe some config value as 示例值 for now, because those config items have no description or default value. Some missing explanations need to be added in new PRs.

cdc: reformat Changefeed config and Server config
ref: pingcap/docs#19522 and pingcap/docs#19521

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 (in Chinese).

• master (the latest development version)
• v8.5 (TiDB 8.5 versions)
• v8.4 (TiDB 8.4 versions)
• v8.3 (TiDB 8.3 versions)
• v8.2 (TiDB 8.2 versions)
• v8.1 (TiDB 8.1 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)

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

• This PR is translated from:
• Other reference link(s): Reformat the config file documentation format of DM, Lightning, TiCDC, TiFlash to the same as that of TiDB, TiKV, PD, TiProxy docs#19005

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

[Oreoxmt]

/approve

[ti-chi-bot]

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