tests/si_utils: error message for quiesce_uploads timeouts

[andijcr]

quiesce_uploads() can timeout for several reasons.
These reasons are logged but the final timeout error does not capture this message.

This pr reports the last message produced while waiting for the last kafka offset to read the high watermark.
hopefully, this should make it slightly easier to differentiate between failure modes

Related to #15310 (comment)

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
• v23.3.x
• v23.2.x
• v23.1.x

Release Notes

• none

[vbotbuildovich]

new failures in https://buildkite.com/redpanda/redpanda/builds/43483#018cda2b-7ea7-4eef-a453-217709b0069a:

"rptest.tests.recovery_mode_test.DisablingPartitionsTest.test_disable"

new failures in https://buildkite.com/redpanda/redpanda/builds/43483#018ce965-f6f6-4542-9ab5-72491515a423:

"rptest.tests.recovery_mode_test.DisablingPartitionsTest.test_disable"

[andijcr]

https://buildkite.com/redpanda/redpanda/builds/43483#018cda2b-7ea7-4eef-a453-217709b0069a failure is #15949