### Motivation
Fixes#6131 (caused by #5675):
When upgrading an existing 2.4.1 bookie cluster to 2.5.0 on kubernetes, the bookie fails to start with the following exception during initialization: io.netty.util.internal.OutOfDirectMemoryError: failed to allocate 16777216 byte(s) of direct memory (used: 2147483648, max: 2147483648). This is caused by the fact that the bookie environment variables `BOOKIE_MEM` and `BOOKIE_FC` defined in conf/bkenv.sh has no effect, and it is always using the defaults values.
#### Proposed solution:
Set `BOOKIE_MEM` and `BOOKIE_GC` in the helm deployments charts and default to `PULSAR_MEM` if the `BOOKIE` settings are not set and then use the default settings if none of those environment variables are set.
#### Changes made
Helm chart deployment `values.yaml` and `values-mini.yaml` along with the `bkenv.sh` configuration script.
### Documentation
Currently, the documentation explaining the deployment process and how to change settings is lacking and need to be updated.
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