Rename the "all" and "any" features to "keyword_all" and "keyword_any"

[book]

According to PSC #180:

We agreed on not terrible feature names for PPC 0027: keyword_any and keyword_all. These can now be merged.

The all and any feature names are confusing (see also the issue around :all #23095). When discussing our options, we agreed that a prefix would be a good option (also making room for more similar features in the future). keyword was the least terrible prefix we came up with.

[leonerd]

Should the warning categories also be renamed? Are the warning categories related to the feature names (i.e. rename to experimental::keyword_all) or the keyword (i.e. remain at experimental::all)?

[mauke]

There are warnings categories like experimental::signatures and experimental::for_list, so I'd say yes, the categories are related to feature names and should be renamed accordingly here.