this is a part of a series migrating from `operator<<(ostream&, ..)` based formatting to fmtlib based formatting. the goal here is to enable fmtlib to print `range_tombstone` and `range_tombstone_change` without using ostream<<. also, this change removes all existing callers of `operator<<(ostream, const range_tombstone &)` and `operator<<(ostream, const range_tombstone_change &)`, and then removes these two `operator<<`s.
Refs #13245Closes#13260
* github.com:scylladb/scylladb:
mutation: drop operator<<(ostream, const range_tombstone{_change,} &)
mutation: use fmtlib to print range_stombstone{_change,}
mutation: mutation_fragment_v2: specialize fmt::formatter<range_tombstone_change>
mutation: range_tombstone: specialize fmt::formatter<range_tombstone>
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