[TASK] Remove extbase Request->setMethod()

To further prepare towards a PSR-7 Request in extbase
we have to get rid of the setMethod() method.

Therefore, the internal method setMethod() is dropped,
while the public getMethod() is adjusted to use
the PSR-7 Request. Additionally, the now unused
InvalidRequestMethodException is deprecated.

Resolves: #94231
Related: #94231
Related: #94223
Releases: master
Change-Id: I1298cd049cf6fc1d44cf46ec3cbb3bd588b3bb7a
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/69319


Tested-by: core-ci <typo3@b13.com>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Daniel Goerz <daniel.goerz@posteo.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Daniel Goerz <daniel.goerz@posteo.de>