feat: new bundle variable - KEYCLOAK_HEAP_OPTIONS

[slaskawi]

Description

This Pull Request introduces KEYCLOAK_HEAP_OPTIONS to control the Java Heap
configuration passed into Keycloak deployments.

Related Issue

Relates to #1309

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Other (security config, docs update, etc)

Steps to Validate

Run the CI and check the Keyclaok Pod Spec

Checklist before merging

• Test, docs, adr added or updated as needed
• Contributor Guide followed

[slaskawi]

Checked the CI logs and the Keycloak Pod configuration seems to be correct:

        - name: JAVA_OPTS_KC_HEAP
          value: -XX:MaxRAMPercentage=70 -XX:MinRAMPercentage=70 -XX:InitialRAMPercentage=50
            -XX:MaxRAM=1G