Implement prepareThreshold to Reduce Unnecessary Server-Side Prepared Statements

Current Implementation

The driver currently uses an LRU cache (size: 256) to store prepared statements. When useServerPrepStmts is enabled, every SQL statement immediately triggers a PREPARE command on the PostgreSQL server, regardless of execution frequency. This approach creates significant overhead:

Extra processing and memory consumption on the server side
Additional network roundtrips for each prepared statement
Resource allocation for queries that may execute only once or twice

Proposed Solution: prepareThreshold Implementation

Implement a threshold-based approach option (default: 5 executions).

Mechanism:

1. Track execution count for each unique SQL statement
2. Send PREPARE command only after the statement has been executed N times
3. Use client-side execution until the threshold is reached
4. Cache prepared statements in the existing LRU cache once the threshold is met

Benefits:

• Server-side preparation limited to frequently executed statements by default
• Fewer roundtrips for infrequently-used queries

Configuration Options
The prepareThreshold parameter provides flexible control:

• 0: Always prepare immediately (equivalent to current useServerPrepStmts=true behavior)
• 1-N: Prepare after N executions (default: 5, recommended)
• -1: Never auto-prepare (equivalent to current useServerPrepStmts=false behavior)

replacing useServerPrepStmts option completly, (even if alias will be keeped for compatibility)