[12.x] Fix QueryException showing wrong connection details for read PDO

[mathiasgrimm]

Previously on this PR we added the connection details to the QueryException, however, it wasn't getting the correct host for the readPdo.

This PR introduced the latestReadWriteTypeUsed() which allows us to know which connection was last used.

This PR

• Fixes QueryException showing write connection details when a query fails on the read PDO connection
• Adds $readPdoConfig property and setReadPdoConfig() method to store read connection configuration
• Updates getConnectionDetails() to return read config when latestReadWriteTypeUsed() === 'read'

Before

When DB::connection('mysql')->select('...', useReadPdo: true) failed, exception showed:
Host: write.host.example (incorrect)

After

Exception correctly shows:
Host: read.host.example

How to reproduce

Connection Error

1. Configure a read/write connection with different hosts in config/database.php:

'mysql' => [
  'read' => ['host' => 'invalid.read.host'],
  'write' => ['host' => 'invalid.write.host'],
  'driver' => 'mysql',
  'database' => 'test_db',
  // ...
],

2. Run a query using the read connection:

DB::connection('mysql')->select('SELECT 1', useReadPdo: true);

Query Error

1. Configure the read connection with valid hosts/credentials and the write connection with invalid host/credentials in config/database.php:

'mysql' => [
  'read' => ['host' => '127.0.0.1'], // valid
  'write' => ['host' => '127.0.0.2'], // invalid
  'driver' => 'mysql',
  'database' => 'test_db',
  // ...
],

2. Run a query using the read connection:

DB::connection('mysql')->select('SELECTINVALID', useReadPdo: true);