Continue the effort of normalizing reader names, stripping legacy qualifying terms like "flat" and "v2".
Flat and v2 readers are the default now, we only need to add qualifying terms to readers which are different than the normal.
One such reader remains: `make_generating_reader_v1()`.
This PR contains mostly mechanical changes, done with a sed script. Commits which only contain such mechanical renames are marked as such in the commitlog.
Code cleanup, no backport needed.
Closesscylladb/scylladb#23767
* github.com:scylladb/scylladb:
readers: mv reversing_v2.hh reversing.hh
readers: mv generating_v2.hh generating.hh
tree: s/make_generating_reader_v2/make_generating_reader/
readers: mv from_mutations_v2.hh from_mutations.hh
tree: s/make_mutation_reader_from_mutations_v2/make_mutation_reader_from_mutations/s
readers: mv from_fragments_v2.hh from_fragments.hh
readers: mv forwardable_v2.hh forwardable.hh
readers: mv empty_v2.hh empty.hh
tree: s/make_empty_flat_reader_v2/make_empty_mutation_reader/
readers/empty_v2.hh: replace forward declarations with include of fwd header
readers/mutation_reader_fwd.hh: forward declare reader_permit
readers: mv delegating_v2.hh delegating.hh
readers/delegating_v2.hh: move reader definition to _impl.hh file
0206da5232