Postgres: Switch the datasource plugin from lib/pq to pgx (#103961)

* Create libpqToPGX feature toggle

* Refactor PostgreSQL datasource to support PGX with feature toggle

- Updated `ProvideService` to accept feature toggles for enabling PGX.
- Modified integration tests to use the new PGX connection method.
- Introduced new functions for handling PGX connections and queries.
- Enhanced TLS configuration handling for PostgreSQL connections.
- Updated existing tests to ensure compatibility with PGX and new connection methods.

* Update PostgreSQL datasource to enhance connection pooling and error handling

- Increased `MaxOpenConns` to 10 in integration tests for improved connection management.
- Refactored connection handling in `newPostgresPGX` to return a connection pool instead of a single connection.
- Updated health check error handling to utilize context and feature toggles for better error reporting.
- Adjusted `DisposePGX` method to close the connection pool properly.
- Enhanced query execution to acquire connections from the pool, ensuring efficient resource usage.

* Cleanup

* Revert postgres_test unnecessary changes

* Rename feature toggle from `libpqToPGX` to `postgresDSUsePGX`

* Add null check to dispose method

* Fix lint issues

* Refactor connection string generation

* Address comment in health check file

* Rename p to pool

* Refactor executeQueryPGX and split into multiple functions

* Fix lint issues

* The returning error message from PGX is enough no need to separate the error code.

* Move TLS handling to newPostgresPGX function

* Disable ssl for integration tests

* Use MaxIdleConns option

* Remove old feature toggle

* Rename`generateConnectionConfigPGX` to `generateConnectionStringPGX`

* Add back part of the error messages

* Don't show max idle connections option when PGX enabled

* Address comments from Sriram

* Add back Sriram's changes

* PostgreSQL: Rework tls manager to use temporary files instead (#105330)

* Rework tls manager to use temporary files instead

* Lint and test fixes

* Update pkg/tsdb/grafana-postgresql-datasource/postgres.go

Co-authored-by: Ivana Huckova <30407135+ivanahuckova@users.noreply.github.com>

* Update betterer

---------

Co-authored-by: Ivana Huckova <30407135+ivanahuckova@users.noreply.github.com>

---------

Co-authored-by: Ivana Huckova <30407135+ivanahuckova@users.noreply.github.com>

pkg/tsdb/grafana-postgresql-datasource/proxy.go

@@ -33,3 +33,11 @@ func (p *postgresProxyDialer) DialTimeout(network, address string, timeout time.
 
 	return p.d.(proxy.ContextDialer).DialContext(ctx, network, address)
 }
+
+type PgxDialFunc = func(ctx context.Context, network string, address string) (net.Conn, error)
+
+func newPgxDialFunc(dialer proxy.Dialer) PgxDialFunc {
+	return func(ctx context.Context, network string, addr string) (net.Conn, error) {
+		return dialer.Dial(network, addr)
+	}
+}