add ZooKeeperSessionExpired metric

[mstetsyuk]

Changelog category (leave one):

• Improvement

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

Add a new ZooKeeperSessionExpired metric which indicates the number of expired global ZooKeeper sessions.

Documentation entry for user-facing changes

• Documentation is written (mandatory for new features)

[clickhouse-gh]

Workflow [PR], commit [2fbdd88]

Summary: ❌

job_name	test_name	status	info	comment
Stateless tests (amd_binary, ParallelReplicas, s3 storage, parallel)		failure
	02788_fix_logical_error_in_sorting	FAIL
	Exception in test runner	FAIL
	Killed by signal (in clickhouse-server.log or clickhouse-server.err.log)	FAIL
	Fatal messages (in clickhouse-server.log or clickhouse-server.err.log)	FAIL
Stress test (amd_tsan)		failure
	Server died	FAIL
	Hung check failed, possible deadlock found (see hung_check.log)	FAIL
	Killed by signal (in clickhouse-server.log)	FAIL
	Fatal message in clickhouse-server.log (see fatal_messages.txt)	FAIL
	Killed by signal (output files)	FAIL
	Found signal in gdb.log	FAIL
AST fuzzer (amd_msan)		failure
	Logical error: 'Column __text_index_idx_fc_hasToken_0 with type Nullable(UInt8) should not be filled by text index reader'.	FAIL