This PR adds an upgrade test for SSTable compression with shared dictionaries, and adds some bits to pylib and test.py to support that.
In the series, we:
1. Mount `$XDG_CACHE_DIR` into dbuild.
2. Add a pylib function which downloads and installs a released ScyllaDB package into a subdirectory of `$XDG_CACHE_DIR/scylladb/test.py`, and returns the path to `bin/scylla`.
3. Add new methods and params to the cluster manager, which let the test start nodes with historical Scylla executables, and switch executables during the test.
4. Add a test which uses the above to run an upgrade test between the released package and the current build.
5. Add `--run-internet-dependent-tests` to `test.py` which lets the user of `test.py` skip this test (and potentially other internet-dependent tests in the future).
(The patch modifying `wait_for_cql_and_get_hosts` is a part of the new test — the new test needs it to test how particular nodes in a mixed-version cluster react to some CQL queries.)
This is a follow-up to #23025, split into a separate PR because the potential addition of upgrade tests to `test.py` deserved a separate thread.
Needs backport to 2025.2, because that's where the tested feature is introduced.
Fixes#24110Closesscylladb/scylladb#23538
* github.com:scylladb/scylladb:
test: add test_sstable_compression_dictionaries_upgrade.py
test.py: add --run-internet-dependent-tests
pylib/manager_client: add server_switch_executable
test/pylib: in add_server, give a way to specify the executable and version-specific config
pylib: pass scylla_env environment variables to the topology suite
test/pylib: add get_scylla_2025_1_executable()
pylib/scylla_cluster: give a way to pass executable-specific options to nodes
dbuild: mount "$XDG_CACHE_HOME/scylladb"
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