Add log level config in pulsar-client (#8195)
Add log level config in pulsar-client (#8195)

### Motivation
When using pulsar-client CLI, we have a lot of log4j logs useless for just sending/receiving messages.
It could great to not display these logs with just a env variable (like in pulsar-admin).

### Modifications
The log level can be configured with the system property `pulsar.log.level` for the Java application.
The modification is the ability to set this level using a env variable PULSAR_LOG_LEVEL (default: info).
massakam/pulsar,merlimat/pulsar,massakam/pulsar,yahoo/pulsar,yahoo/pulsar,merlimat/pulsar,yahoo/pulsar,massakam/pulsar,merlimat/pulsar,massakam/pulsar,massakam/pulsar,massakam/pulsar,merlimat/pulsar,merlimat/pulsar,yahoo/pulsar,merlimat/pulsar,yahoo/pulsar,yahoo/pulsar