[Good First Issue] Add Consumer Percentage Control for Catch-up Reading in Performance Test

[Chillax-0v0]

Background

AutoMQ provides the automq-perf-test.sh script to test performance under different scenarios. Currently, it supports testing "catch-up read" (cold read) scenarios by:

1. Sending a batch of messages.
2. Delaying consumption until messages have accumulated for a specified period.
3. Observing consumption throughput and its impact on producers.

However, the current implementation starts all consumers simultaneously, which does not reflect real-world scenarios where only a subset of topics experience catch-up reads at the same time.

Required Changes

Add a new optional command-line argument (e.g., --consumers-during-catchup) to the automq-perf-test.sh script to control the num of consumers activated during catch-up read scenarios.

[Dr-Maple]

/assign

[harry-xiao-xin]

/assign