[TASK] Avoid calls to TemplatePaths constructor

The constructor of Fluid's `TemplatePath` class allowed
both a package name and a configuration array (containing
`templateRootPaths`, `layoutRootPaths`, `partialRootPaths`
and a `format`). It also tried to set defaults for TYPO3,
without the base `TemplatePaths` class being part of TYPO3.

To streamline Fluid's API and to untangle Fluid's configuration
from TYPO3, both constructor variants have been soft-deprecated
with Fluid v2.15 and will log deprecation notices with Fluid v4.
In preparation of the switch to Fluid v4, all usages of the
constructor are removed from the core. A lot of this work
has already been done in previous patches.

The remaining usages are related to the `FluidEmail` class,
which unfortunately uses Fluid's `TemplatePaths` class as
API. In all cases, the default mailer configuration is extended,
which is part of the system configuration:

from DefaultConfiguration.php:

```
    'MAIL' => [ // Mail configurations to tune how \TYPO3\CMS\...