Do not run Cloud tests by default with external PRs or commits

When a PR is created by an external contributor, the GHA cannot pull the secrets required to access the ClickHouse Cloud instance, and the CI run fails.

The simplest solution is to disable automatic Cloud tests if a PR or commit was submitted by a user who is not a member of the CH organization.

See the CI source: https://github.com/ClickHouse/clickhouse-js/blob/1.12.1/.github/workflows/tests.yml#L196-L252

Note that it should still do the codecov check.