tests: wait for stable metrics in delayed enablement test

[mmaslankaprv]

Sometimes the metrics queried from Redpanda are not fully reported. This makes the test to fail intermittently. Changed the way metrics are queried to wait for the reported metrics value to quiesce before performing validation.

Backports Required

• none - not a bug fix
• none - this is a backport
• none - issue does not exist in previous branches
• none - papercut/not impactful enough to backport
• v25.1.x
• v24.3.x
• v24.2.x

Release Notes

• none

[vbotbuildovich]

CI test results

test results on build#67997

test_class	test_method	test_arguments	test_kind	job_url	test_status	passed	reason
TestMirrorMakerService	test_simple_end_to_end	{"source_type": "kafka"}	ducktape	https://buildkite.com/redpanda/redpanda/builds/67997#0197ad38-82ef-4d17-8e89-4bef2c16447c	FLAKY	20/21	upstream reliability is '100.0'. current run reliability is '95.23809523809523'. drift is 4.7619 and the allowed drift is set to 50. The test should PASS
NodePoolMigrationTest	test_migrating_redpanda_nodes_to_new_pool	{"balancing_mode": "node_add", "cleanup_policy": "compact,delete", "test_mode": "tiered_storage_fast_moves"}	ducktape	https://buildkite.com/redpanda/redpanda/builds/67997#0197ad32-3905-4cb7-9d24-bd718045e869	FLAKY	20/21	upstream reliability is '99.68152866242038'. current run reliability is '95.23809523809523'. drift is 4.44343 and the allowed drift is set to 50. The test should PASS
RandomNodeOperationsTest	test_node_operations	{"cloud_storage_type": 2, "compaction_mode": "chunked_sliding_window", "enable_failures": true, "mixed_versions": false, "with_iceberg": false}	ducktape	https://buildkite.com/redpanda/redpanda/builds/67997#0197ad32-38fb-4c8e-9e70-5bce5095f75d	FLAKY	20/21	upstream reliability is '99.27272727272727'. current run reliability is '95.23809523809523'. drift is 4.03463 and the allowed drift is set to 50. The test should PASS
RpkToolTest	test_analyze		ducktape	https://buildkite.com/redpanda/redpanda/builds/67997#0197ad38-82f5-4485-8291-b90d48a1a15c	FLAKY	20/21	upstream reliability is '98.01136363636364'. current run reliability is '95.23809523809523'. drift is 2.77327 and the allowed drift is set to 50. The test should PASS

[vbotbuildovich]

/backport v25.1.x

[vbotbuildovich]

Failed to create a backport PR to v25.1.x branch. I tried:

git remote add upstream https://github.com/redpanda-data/redpanda.git
git fetch --all
git checkout -b backport-pr-26600-v25.1.x-48 remotes/upstream/v25.1.x
git cherry-pick -x dff076d62b

Workflow run logs.