Test 2MB for topic_memory_per_partition

[mfleming]

See whether MPT will run if we reduce topic_memory_per_partition from 4MB to 2MB. This will include:

• passing topic_memory_per_partition from MPT to the RP config.
• Using @parametrize(mb_per_partition=2) with MPT to make future testing easier

Expected outcome

• RP shouldn't crash due to OOM ;)
• The amount of memory given to each broker (by MPT) should be 2 1000 4 MiB or 7.81GiB for i3en.xlarge.
• All MPT tests should pass unless marked @ok_to_fail

JIRA Link: CORE-1596

[StephanDollberg]

2MB@2000 partitions have been working in the MPT non-TS tests.

[calvin2021y]

any update?