[#10472] feat(entity store): support entity store read-replica connections

[youngyjd]

What changes were proposed in this pull request?

1. Add optional read-replica support for the relational entity store (JDBCBackend): new config keys for read-only JDBC URL, user, password, and pool sizing (or inherit from primary).
2. When any read-only config is set, create a second JDBC pool and route standalone metadata reads to it; keep writes and in-transaction reads on the primary pool.
3. Add startup log when the read pool is enabled and optional metrics for the read datasource; leave behavior unchanged when read-only config is not set.

Why are the changes needed?

To allow offloading read-heavy metadata traffic to a read replica (e.g. MySQL) instead of the primary, improving scalability and reducing load on the primary while keeping writes and transactional reads on the primary.

Fix: #10472

Does this PR introduce any user-facing change?

Yes. New optional configuration options for the relational backend (jdbcReadOnlyUrl, jdbcReadOnlyUser, jdbcReadOnlyPassword, readOnlyMaxConnections, readOnlyMaxWaitMillis) and optional metrics for the read pool. Existing deployments are unchanged unless these options are set.

How was this patch tested?

1. unit tested
2. existing integration guarantees backward compatibility

[github-actions]

Code Coverage Report

Overall Project	64.96% +0.21%	🟢
Files changed	92.42%	🟢

Module	Coverage
aliyun	1.73%	🔴
api	47.14%	🟢
authorization-common	85.96%	🟢
aws	1.1%	🔴
azure	2.6%	🔴
catalog-common	10.0%	🔴
catalog-fileset	80.02%	🟢
catalog-hive	80.98%	🟢
catalog-jdbc-clickhouse	78.25%	🟢
catalog-jdbc-common	42.98%	🟢
catalog-jdbc-doris	80.28%	🟢
catalog-jdbc-hologres	54.03%	🟢
catalog-jdbc-mysql	79.23%	🟢
catalog-jdbc-oceanbase	78.38%	🟢
catalog-jdbc-postgresql	82.05%	🟢
catalog-jdbc-starrocks	78.27%	🟢
catalog-kafka	77.01%	🟢
catalog-lakehouse-generic	45.07%	🟢
catalog-lakehouse-hudi	79.1%	🟢
catalog-lakehouse-iceberg	87.15%	🟢
catalog-lakehouse-paimon	77.71%	🟢
catalog-model	77.72%	🟢
cli	44.51%	🟢
client-java	77.83%	🟢
common	49.36%	🟢
core	81.35% +0.28%	🟢
filesystem-hadoop3	76.97%	🟢
flink	38.86%	🔴
flink-runtime	0.0%	🔴
gcp	14.2%	🔴
hadoop-common	10.39%	🔴
hive-metastore-common	45.82%	🟢
iceberg-common	50.21%	🟢
iceberg-rest-server	66.24%	🟢
integration-test-common	0.0%	🔴
jobs	66.17%	🟢
lance-common	23.78%	🔴
lance-rest-server	57.84%	🟢
lineage	53.02%	🟢
optimizer	82.87%	🟢
optimizer-api	21.95%	🔴
server	85.65%	🟢
server-common	69.72%	🟢
spark	32.79%	🔴
spark-common	39.6%	🔴
trino-connector	31.62%	🔴

Files

Module	File	Coverage
common	ConfigConstants.java	0.0%	🔴
core	Configs.java	98.26%	🟢
	SqlSessionFactoryHelper.java	92.59%	🟢
	MetricsSource.java	86.36%	🟢
	SessionUtils.java	85.37%	🟢
	SqlSessions.java	84.93%	🟢
	RelationDatasourceMetricsSource.java	0.0%	🔴