[WFLY-1878] : Make concurrency items in ee subsystem use KeepAliveTimeAttributeDefinition

New AttributeDefinition type with a ParameterValidator to transform attribute into the correct value and an OperationTransformer to be able to have 2 ways to define the value.
Jira: https://issues.jboss.org/browse/WFLY-18784
It requires last wildfly-core version since it is using chained transformers.