rpk: topic describe --regex supports internal topics

[daisukebe]

With the --regex flag, rpk filters out internal topics, e.g. __consumer_offsets, but typically we want to see those topics too. With this PR, it no longer filers out internal topics.

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
• v24.2.x
• v24.1.x
• v23.3.x

Release Notes

• none

[daisukebe]

Looks like the 404 error is irrelevant? @r-vasquez

[vbotbuildovich]

ducktape was retried in https://buildkite.com/redpanda/redpanda/builds/55038#01922516-92ef-48e6-9c86-ec1712ba2c28

ducktape was retried in https://buildkite.com/redpanda/redpanda/builds/55038#01922517-442f-48f9-97a1-a99a82dd0dd9

[vbotbuildovich]

new failures in https://buildkite.com/redpanda/redpanda/builds/55038#01922516-92ec-4ea0-b1ec-9ab151029a46:

"rptest.tests.partition_force_reconfiguration_test.PartitionForceReconfigurationTest.test_basic_reconfiguration.acks=-1.restart=False.controller_snapshots=False"

[daisukebe]

Closed as #23487 is done.