filesystem: revamp module (#2472) (#2550)

* revamp filesystem module to prepare next steps

* pass all commands to module.run_command() as lists
* refactor grow() and grow_cmd() to not need to override them so much
* refactor all existing get_fs_size() overrides to raise a ValueError if
  not able to parse command output and return an integer.
* override MKFS_FORCE_FLAGS the same way for all fstypes that require it
* improve documentation of limitations of the module regarding FreeBSD
* fix indentation in DOCUMENTATION
* add/update function/method docstrings
* fix pylint hints

filesystem: refactor integration tests

* Include *reiserfs* and *swap* in tests.
* Fix reiserfs related code and tests accordingly.
* Replace "other fs" (unhandled by this module), from *swap* to *minix*
  (both mkswap and mkfs.minix being provided by util-linux).
* Replace *dd* commands by *filesize* dedicated module.
* Use FQCNs and name the tasks.
* Update main tests conditionals.

* add a changelog fragment

* Apply suggestions from code review

Co-authored-by: Felix Fontein <felix@fontein.de>

* declare variables as lists when lists are needed

* fix construction without useless conversion

Co-authored-by: Felix Fontein <felix@fontein.de>
(cherry picked from commit f6db0745fc)

Co-authored-by: quidame <quidame@poivron.org>

changelogs/fragments/2472_filesystem_module_revamp.yml

@@ -0,0 +1,9 @@
+---
+minor_changes:
+  - "filesystem - cleanup and revamp module, tests and doc. Pass all commands to
+    ``module.run_command()`` as lists. Move the device-vs-mountpoint logic to
+    ``grow()`` method. Give to all ``get_fs_size()`` the same logic and error
+    handling. (https://github.com/ansible-collections/community.general/pull/2472)."
+bugfixes:
+  - "filesystem - repair ``reiserfs`` fstype support after adding it to integration
+    tests (https://github.com/ansible-collections/community.general/pull/2472)."