refactor: consolidate PostgreSQL version constant

[xiangjinwu]

risingwave/src/utils/pgwire/src/pg_protocol.rs

Line 844 in 0d549d7

BeParameterStatusMessage::ServerVersion("9.5.0"),

risingwave/src/common/src/session_config/mod.rs

Line 405 in 0d549d7

#[educe(Default(expression = "ConfigString::<SERVER_VERSION>(String::from(\"9.5.0\"))"))]

risingwave/src/common/src/session_config/mod.rs

Line 302 in 0d549d7

type ServerVersionNum = ConfigI32<SERVER_VERSION_NUM, 90_500>;

risingwave/src/frontend/src/binder/expr/function.rs

Line 965 in 0d549d7

"PostgreSQL 9.5-RisingWave-{} ({})",

[xiangjinwu]

• The frontend version() function now binds to risingwave_common::current_cluster_version
• The pgwire implementation shall read from session.config rather than hardcoding, for all ParameterStatus message not limited to server_version.

[yufansong]

Disscussed offline, 2 action needed:

1. function / streaming job / ddl controller should get version from the same place, which currently is current_cluster_version. Need to set a const in common as the single source of truth. All previous and the ConfigMap should read from there: function/streaming/ddl -> current_cluster_version -> hardcode const in common <- ConfigMap <- pgwire/show. Need to figure out how to read const in ConfigMap
2. Need add a code path in pgwire for ParameterStatus, server version / client encoding / StandardConformingString / ApplicationName need read from config map.