Improve custom entrypoint configuration documentation for JIB images

[schmittjoaopedro]

Description

By looking at the JIB's documentation on configuring custom entry points JIB Docs there is not enough information on the different ways you can configure custom startup scripts for ubi8/openjdk-11-runtime or ubi8/openjdk-17-runtime images, I mean it´s quite challenging to find the right way to set the values to customize the entry point.

Implementation ideas

For example, the documentation could be improved to provide two ways of configuring it:

1. Configuring an in-line entry point start-up command in the application.properties file:

quarkus.jib.jvm-entrypoint=java,-agentlib:jdwp=transport=dt_socket\\,server=y\\,suspend=n\\,address=*:5005,-jar,quarkus-run.jar

2. Creating a custom startup file at src/main/jib/jboss/home/run-java.sh with some content like below:

java \
  -Djavax.net.ssl.trustStore=/deployments/truststore \
  -Djavax.net.ssl.trustStorePassword=$TRUST_STORE_PASSWORD \
  -agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=*:5005 \
  -jar quarkus-run.jar

and providing the custom jvm-entrypoint configuration quarkus.jib.jvm-entrypoint=/bin/sh,run-java.sh

[quarkus-bot]

/cc @geoand

[geoand]

@schmittjoaopedro would you like to contribute the docs improvement you have in mind? This is the doc that would need to be updated

[schmittjoaopedro]

Hi @geoand , of course, I'll create a PR for it.