[TASK] Don't mark ConnectionPool::getConnectionByName() as internal

The method ConnectionPool::getConnectionByName() is no longer flagged
as internal as it is useful for extensions creating connections
to external databases.

Resolves: #84100
Releases: master, 8.7
Change-Id: I9bbf524905c436097264c465e92d8b689994c253
Reviewed-on: https://review.typo3.org/55986


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Daniel Goerz <ervaude@gmail.com>
Tested-by: Daniel Goerz <ervaude@gmail.com>
Reviewed-by: Mathias Brodala <mbrodala@pagemachine.de>
Tested-by: Mathias Brodala <mbrodala@pagemachine.de>
Reviewed-by: Frank Naegler <frank.naegler@typo3.org>
Tested-by: Frank Naegler <frank.naegler@typo3.org>