Drop excess connection limit rate to 2

Default value of 10 can produce up to 900 excess connections on big
nodes.
Let's set it to something safer.

tests: update klauspost/compress to v1.18.1

Main module is already on v1.18.1, no reason to keep tests on old
version.

tests: replace DATEOF with toTimestamp on cassandra >=4.1

Cassandra after 4.1 dropped DATEOF in favor of toTimestamp.
Test needs to be adopted.

Merge pull request #541 from dkropachev/dk/make-unit-test-fail-when-t…

…est-fails

Make `make test-unit` to fail when `go test` fails

Merge pull request #502 from dgarcia360/docs-add-toolchain

docs: add sample site

Merge pull request #499 from dkropachev/dk/generalize-application-inf…

…ormation-api

cluster: generalize application information API

Merge pull request #452 from dkropachev/dk/fix-token-aware-policy-ini…

…tialization

Fix token aware policy initialization

Merge pull request #384 from illia-li/il/add/tests/db_serialization

Add `scylla` serialization tests

Merge pull request #269 from scylladb/gc_docker_image

Add workflow to delete old docker images

Merge pull request #225 from dkropachev/dk/add-iter-docs

Add iterator docs