feat(database/gdb): add MaxIdleConnTime configuration for SetConnMaxIdleTime support

[lingcoder]

Summary

• Add MaxIdleConnTime configuration field to support Go 1.15+ sql.DB.SetConnMaxIdleTime() method
• Add SetMaxIdleConnTime() method to DB interface and Core implementation
• Apply configuration during connection pool initialization
• Add unit tests for the new configuration option

Related Issue

Closes #4596

Changes

File	Change
database/gdb/gdb_core_config.go	Add MaxIdleConnTime field to ConfigNode, add SetMaxIdleConnTime() method
database/gdb/gdb.go	Add interface method, dynamicConfig field, initialization logic
database/gdb/gdb_z_core_config_test.go	Add unit test for SetMaxIdleConnTime
database/gdb/gdb_z_core_config_external_test.go	Add ConfigNode connection pool settings test

Usage

Configuration file:

database:
  default:
    maxIdleTime: "10s"  # Close idle connections after 10 seconds

Code:

db.SetMaxIdleConnTime(10 * time.Second)

Test Plan

• Unit tests pass (go test -run "Test_Core_SetMaxConnections|Test_ConfigNode_ConnectionPoolSettings")
• All database drivers compile successfully (mysql, pgsql, sqlite, clickhouse, dm, mssql, oracle, etc.)
• No breaking changes - follows Go's default behavior (0 = no idle time limit)

[Copilot]

Pull request overview

This PR adds support for configuring the maximum idle time for database connections through the MaxIdleConnTime configuration field, enabling use of Go 1.15+'s sql.DB.SetConnMaxIdleTime() method.

Changes:

• Added MaxIdleConnTime configuration field and setter method to support idle connection timeout
• Integrated the new configuration into the connection pool initialization logic
• Added comprehensive unit tests for the new functionality

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
database/gdb/gdb_core_config.go	Added MaxIdleConnTime field to ConfigNode struct and implemented SetMaxIdleConnTime() method with documentation
database/gdb/gdb.go	Added interface method, MaxIdleConnTime field to dynamicConfig, and initialization logic in getSqlDb()
database/gdb/gdb_z_core_config_test.go	Added unit test for SetMaxIdleConnTime() method in existing connection settings test
database/gdb/gdb_z_core_config_external_test.go	Added comprehensive test for all connection pool configuration fields including MaxIdleConnTime

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