* Create metrics package

* Create metric.py

* Create utils.py

* Create __init__.py

* add tests for metric utils

* add docstrings for metrics utils

* add function to recursively apply other function to collection

* add tests for this function

* update test

* Update pytorch_lightning/metrics/metric.py

Co-Authored-By: Jirka Borovec <Borda@users.noreply.github.com>

* update metric name

* remove example docs

* fix tests

* add metric tests

* fix to tensor conversion

* fix apply to collection

* Update CHANGELOG.md

* Update pytorch_lightning/metrics/metric.py

Co-Authored-By: Jirka Borovec <Borda@users.noreply.github.com>

* remove tests from init

* add missing type annotations

* rename utils to convertors

* Create metrics.rst

* Update index.rst

* Update index.rst

* Update pytorch_lightning/metrics/convertors.py

Co-Authored-By: Jirka Borovec <Borda@users.noreply.github.com>

* Update pytorch_lightning/metrics/convertors.py

Co-Authored-By: Jirka Borovec <Borda@users.noreply.github.com>

* Update pytorch_lightning/metrics/convertors.py

Co-Authored-By: Jirka Borovec <Borda@users.noreply.github.com>

* Update pytorch_lightning/metrics/metric.py

Co-Authored-By: Jirka Borovec <Borda@users.noreply.github.com>

* Update tests/utilities/test_apply_to_collection.py

Co-Authored-By: Jirka Borovec <Borda@users.noreply.github.com>

* Update tests/utilities/test_apply_to_collection.py

Co-Authored-By: Jirka Borovec <Borda@users.noreply.github.com>

* Update tests/metrics/convertors.py

Co-Authored-By: Jirka Borovec <Borda@users.noreply.github.com>

* Apply suggestions from code review

Co-Authored-By: Jirka Borovec <Borda@users.noreply.github.com>

* add doctest example

* rename file and fix imports

* added parametrized test

* replace lambda with inlined function

* rename apply_to_collection to apply_func

* Separated class description from init args

* Apply suggestions from code review

Co-Authored-By: Jirka Borovec <Borda@users.noreply.github.com>

* adjust random values

* suppress output when seeding

* remove gpu from doctest

* Add requested changes and add ellipsis for doctest

* forgot to push these files...

* add explicit check for dtype to convert to

* fix ddp tests

* remove explicit ddp destruction

Co-authored-by: Jirka Borovec <Borda@users.noreply.github.com>

Co-authored-by: Adrian Wälchli <aedu.waelchli@gmail.com>