DOC-5475: Remove unnecessary version information

[simon-dew]

Docs issue: DOC-5475

• Removed (Introduced in ...) captions for versions earlier than 6.5.
• Removed :page-status: attribute for versions earlier than 6.5.
• Removed section status role for features that were not specific to a patch release.

The orange status label should now only appear in the following cases:

1. For pages only: to show that this feature is new in the current version.
2. For pages only: to show that this feature is specific to a developer preview.
3. For sections within a page: to show that a feature is specific to a patch release.

The italic (Introduced in ...) caption should now only appear in the following cases:

1. For sections within a page: to show that this feature is new in the current version.

Anecdotal comments about versions, e.g. "Since Couchbase Server 5.5, you can..." still occur in the running text — I think this is okay.

[simon-dew]

I also added ifeval::['{page-component-version}' == '6.5'] directives to future-proof any captions stating (Introduced in Couchbase Server 6.5). This means that when we create the release/6.6 branch, these captions will be hidden automatically.

[amarantha-k]

Thanks for taking care of these! lgtm