YTSaurus Redirect heavy requests to heavy proxies.

[MikhailBurdukov]

From ytsaurus doc: https://ytsaurus.tech/docs/en/user-guide/proxy/http-reference#hosts
All YTsaurus commands are classified into two groups: light and heavy. Heavy commands are associated with a large I/O and, consequently, a network load. To isolate this load, light (controlling) commands are separated from the heavy ones. When you try to execute a heavy command, light proxies return code 503. The balancing of heavy commands among heavy proxies is performed by the client.

Before you execute a heavy command, you need to query /hosts and get a list of proxies ordered by load. The load is estimated based on the current CPU and network load, as well as some planned future load on the proxies. The very first proxy in the resulting list is the least loaded, and that's the one you want to use in simple cases (= in 80% of cases).

Changelog category (leave one):

• Improvement

Changelog entry (a user-readable short description of the changes that goes into CHANGELOG.md):

Redirect heavy ytsaurus requests to heavy proxies.

Documentation entry for user-facing changes

• Documentation is written (mandatory for new features)

[clickhouse-gh]

Workflow [PR], commit [9b47596]

Summary: ❌

job_name	test_name	status	info	comment
Stateless tests (amd_binary, old analyzer, s3 storage, DatabaseReplicated, parallel)		failure
	01201_read_single_thread_in_order	FAIL