This series adds two commands:
* scylla sstable-summary
* scylla sstable-index-cache
The former dumps the content of the sstable summary. This component is kept in memory in its entirety, so this can be easily done. The latter command dumps the content of the sstable index cache. This contains all the index-pages that are currently cached. The promoted index is not dumped yet and there is no indication of whether a given entry is in the LRU or not, but this already allows at seeing what pages are in the cache and what aren't.
Closes#10546
* github.com:scylladb/scylla:
scylla-gdb.py: add scylla sstable-index-cache command
scylla-gdb.py: add scylla sstable-summary command
test/scylla-gdb: add sstable fixture
scylla-gdb.py: make chunked_vector a proper container wrapper"
scylla-gdb.py: make small_vector a proper container wrapper"
scylla-gdb.py: add sstring container wrapper
scylla-gdb.py: add chunked_managed_vector container wrapper
scylla-gdb.py: add managed_vector container wrapper
scylla-gdb.py: std_variant: add workaround for clang template bug
scylla-gdb.py: add bplus_tree container wrapper