Remove duplicate setup and teardown functions (#19254)

* Remove duplicate setup and teardown functions

faccd91071cc34ed0b3a192d3c7932441fe7e35e introduced a automatic pytest hooks for
handling MXNET_MODULE_SEED adapted from
https://github.com/dmlc/gluon-nlp/commit/66e926a5e3e630dcf11ebbfba6c7948645abcf56
but didn't remove the existing seed handling via explicit setup and teardown
functions.

This commit removes the explicit setup and teardown functions in favor of the
automatic pytest version, and thereby also ensures that the seed handling code
is not executed twice. As a side benefit, seed handling now works correctly even
if contributors forget to add the magic setup_module and teardown_module
imports in new test files.

If pytest is run with --capture=no (or -s shorthand), output of the module level
fixtures is shown to the user.

* Fix locale setting