There are tons of wrappers that help test cases make sstables for their needs. And lots of code duplication in test cases that do parts of those helpers' work on their own. This set cleans some bits of those
Closes#14280
* github.com:scylladb/scylladb:
test/utils: Generalize making memtable from vector<mutation>
test/util: Generalize make_sstable_easy()-s
test/sstable_mutation: Remove useless helper
test/sstable_mutation: Make writer config in make_sstable_mutation_source()
test/utils: De-duplicate make_sstable_containing-s
test/sstable_compaction: Remove useless one-line local lambda
test/sstable_compaction: Simplify sstable making
test/sstables*: Make sstable from vector of mutations
test/mutation_reader: Remove create_sstable() helper from test
bd7a3e5871