[v24.1.x] pandaproxy: add missing internal metrics

[IoannisRP]

Backport of PR #24564

[vbotbuildovich]

Retry command for Build#59856

please wait until all jobs are finished before running the slash command

/ci-repeat 1
tests/rptest/tests/nodes_decommissioning_test.py::NodesDecommissioningTest.test_decommissioning_and_upgrade

[vbotbuildovich]

CI test results

test results on build#59856

test_id	test_kind	job_url	test_status	passed
rptest.tests.nodes_decommissioning_test.NodesDecommissioningTest.test_decommissioning_and_upgrade	ducktape	https://buildkite.com/redpanda/redpanda/builds/59856#0193d519-9292-4cec-8849-ba8c6fc6b8dd	FAIL	0/1

test results on build#59876

test_id	test_kind	job_url	test_status	passed
rptest.tests.topic_recovery_test.TopicRecoveryTest.test_time_based_retention.cloud_storage_type=CloudStorageType.S3	ducktape	https://buildkite.com/redpanda/redpanda/builds/59876#0193d628-227f-47ff-9149-727ad3acb6f0	FAIL	0/1

[vbotbuildovich]

Retry command for Build#59876

please wait until all jobs are finished before running the slash command

/ci-repeat 1
tests/rptest/tests/topic_recovery_test.py::TopicRecoveryTest.test_time_based_retention@{"cloud_storage_type":1}