This PR removes information about outdated versions, including disclaimers and information when a given feature was added.
Now that the documentation is versioned, information about outdated versions is unnecessary (and makes the docs harder to read).
Fixes https://github.com/scylladb/scylladb/issues/12110Closesscylladb/scylladb#17430
The goal is to make the available defaults safe for future use, as they
are often taken from existing config files or documentation verbatim.
Referenced issue: #14290Closesscylladb/scylladb#15947
The DML page is quite long (21 screenfuls on my monitor); split
it into one page per statement to make it more digestible.
The sections that are common to multiple statement are kept
in the main DML page, and references to them are added.
Closes#15053
