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>

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

pkg/tsdb/grafana-postgresql-datasource/sqleng/sql_engine.go

@@ -19,6 +19,7 @@ import (
 	"github.com/grafana/grafana-plugin-sdk-go/backend/log"
 	"github.com/grafana/grafana-plugin-sdk-go/data"
 	"github.com/grafana/grafana-plugin-sdk-go/data/sqlutil"
+	"github.com/jackc/pgx/v5/pgxpool"
 )
 
 // MetaKeyExecutedQueryString is the key where the executed query should get stored
@@ -88,6 +89,7 @@ type DataSourceHandler struct {
 	dsInfo                 DataSourceInfo
 	rowLimit               int64
 	userError              string
+	pool                   *pgxpool.Pool
 }
 
 type QueryJson struct {
@@ -489,6 +491,7 @@ type dataQueryModel struct {
 	Interval          time.Duration
 	columnNames       []string
 	columnTypes       []*sql.ColumnType
+	columnTypesPGX    []string
 	timeIndex         int
 	timeEndIndex      int
 	metricIndex       int