[fix] Remove gcompat from the Alpine based image since real glibc is installed

[lhotari]

Motivation

In 3.3.1 and 4.0.0-preview.1 images, Conscrypt cannot be loaded. Jetty uses it for native OpenSSL based TLS.
This caused a problem described in #23364 where the warning log message "2024-09-27T19:25:20,336+0000 [main] WARN org.apache.pulsar.common.util.SecurityUtility - Conscrypt isn't available for Linux amd64. Using JDK default security provider." broke pulsar-admin output parsing in other scripts.
The problem was addressed by setting log level to debug.

While investigating the issue, it appeared that musl + gcompat and glibc in Alpine shouldn't be mixed at runtime in dynamic linking. It's not recommended to mix musl and glibc either.

However, for the Conscrypt case, the loading of the library works when gcompat is removed. There shouldn't be a reason to have gcompat exist with the current real glibc solution in Alpine.

Modifications

• remove gcompat package from Alpine.

Documentation

• doc
• doc-required
• doc-not-needed
• doc-complete

[lhotari]

IIRC, the reason to add real glibc support was due to the fact that the Pulsar IO Kinesis connector didn't work with the Alpine image. The Kinesis connector uses Amazon Kinesis Producer which contains an embedded native application that has been compiled for glibc.
https://github.com/awslabs/amazon-kinesis-producer/blob/3be1d3d6e77ffa80eb173fd7e06ac962db6ec6b1/java/amazon-kinesis-producer/src/main/java/com/amazonaws/services/kinesis/producer/Daemon.java#L429-L461

There's a script in the repository to compile it for other runtime environments: https://github.com/awslabs/amazon-kinesis-producer/blob/master/bootstrap.sh

For using amazon-kinesis-producer, the correct approach would be to have build a musl compatible binary or have a solution to run the process in an isolated glibc environment. It would be possible to build a minimal environment with the minimal set of libraries and then pass LD_LIBRARY_PATH environment variable to use it for running the kinesis_producer binary. The current library already supports overriding the binary and passing environment variables.