* seastar e708d1df3a...92365e7b87 (11):
> tests: distributed_test: convert to SEASTAR_TEST_CASE
> Merge "Avoid undefined behavior on future self move assignments" from Rafael
> Merge "C++20 support" from Avi
> optimized_optional: don't use experimental C++ features
> tests: scheduling_group_test: verify that later() doesn't modify the current group
> tests: demos: coroutine_demo: add missing include for open_file_dma()
> rpc: minor documentation improvements
> rpc: Assert that sinks are closed
> Merge "Fix most tests under valgrind" from Rafael
> distributed_test: Fix it on slow machines
> rpc_test: Make sure we always flush and close the sink
loading_shard_values.hh: added missing include for gcc6-concepts.hh,
exposed by the submodule update.
Frozen toolchain updated for the new valgrind dependency.
e774ee06ed