[APIM-4.0.0] Invalid username reference for TopicConnectionFactory url in jndi-cp.properties.j2

[chaminda]

Description:

Currently, jndi-cp.properties.j2 file is referring only the apim.event_hub.username as the username to construct the TopicConnectionFactory when some conditions are true. This will break the configuration if email user is enabled in the deployment.toml and also when event_hub configurations are applied(TM seperation use case)
It will result constructing the endpoint setting the username as admin@wso2.com@carbon.super
Ideally this value should be admin!wso2.com!carbon.super to be success with the configurations.
Hence we need to refer apim.throttling.jms.username instead.

Steps to reproduce:

1. Configure APIM-4.0.0 with email-user enabled configs
2. Apply event_hub configurations.
3. Start the server and check jndi-cp.properties file.

Affected Product Version:

APIM-4.0.0

Environment details (with versions):

N/A