Revisit transactional advice around job repository methods

[fmbenhassine]

The transactional proxy created around the job repository in AbstractJobRepositoryFactoryBean is not accurate/optimized:

spring-batch/spring-batch-core/src/main/java/org/springframework/batch/core/repository/support/AbstractJobRepositoryFactoryBean.java

Lines 198 to 208 in d95397f

	if (this.transactionAttributeSource == null) {
	Properties transactionAttributes = new Properties();
	transactionAttributes.setProperty("create*",
	TRANSACTION_PROPAGATION_PREFIX + Propagation.REQUIRES_NEW + "," + this.isolationLevelForCreate);
	transactionAttributes.setProperty("getLastJobExecution*",
	TRANSACTION_PROPAGATION_PREFIX + Propagation.REQUIRES_NEW + "," + this.isolationLevelForCreate);
	transactionAttributes.setProperty("*", "PROPAGATION_REQUIRED");
	this.transactionAttributeSource = new NameMatchTransactionAttributeSource();
	((NameMatchTransactionAttributeSource) this.transactionAttributeSource)
	.setProperties(transactionAttributes);
	}

For example, some methods (like get* and find*) could be marked as read-only.

v6 is a good opportunity to revisit and optimise this.