KAFKA-19011 Improve EndToEndLatency Tool with argument parser and message key/header support (apache#20301)

jira: https://issues.apache.org/jira/browse/KAFKA-19011  kip:

https://cwiki.apache.org/confluence/display/KAFKA/KIP-1172%3A+Improve+EndToEndLatency+tool

This PR improves the usability and maintainability of the
`kafka-e2e-latency.sh` tool:

- Replaces fixed-index argument parsing with a proper argument parser
(joptsimple)
- Adds support for configuring:
    - -record-key-size: size of the message key
    - -num-headers: number of headers per message
    - -record-header-key-size: size of each header key
    - -record-header-size: size of each header value
- Renames existing arguments to align with Kafka CLI conventions:
    - broker_list → bootstrap-server
    - num_messages → num-records
    - message_size_bytes → record-size
    - properties_file → command-config
    -

Reviewers: Jhen-Yung Hsu <jhenyunghsu@gmail.com>, Ken Huang
 <s7133700@gmail.com>, Chia-Ping Tsai <chia7712@gmail.com>

Author: Rancho-7