char: misc: add test cases

Add test cases for static and dynamic minor number allocation and
deallocation.

While at it, improve description and test suite name.

Some of the cases include:

- that static and dynamic allocation reserved the expected minors.

- that registering duplicate minors or duplicate names will fail.

- that failing to create a sysfs file (due to duplicate names) will
  deallocate the dynamic minor correctly.

- that dynamic allocation does not allocate a minor number in the static
  range.

- that there are no collisions when mixing dynamic and static allocations.

- that opening devices with various minor device numbers work.

- that registering a static number in the dynamic range won't conflict with
  a dynamic allocation.

This last test verifies the bug fixed by commit 6d04d2b554 ("misc:
misc_minor_alloc to use ida for all dynamic/misc dynamic minors") has not
regressed.

Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@igalia.com>
Link: https://lore.kernel.org/r/20250612-misc-dynrange-v5-1-6f35048f7273@igalia.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

lib/Kconfig.debug

@@ -2506,8 +2506,8 @@ config TEST_IDA
 	tristate "Perform selftest on IDA functions"
 
 config TEST_MISC_MINOR
-	tristate "miscdevice KUnit test" if !KUNIT_ALL_TESTS
-	depends on KUNIT
+	bool "miscdevice KUnit test" if !KUNIT_ALL_TESTS
+	depends on KUNIT=y
 	default KUNIT_ALL_TESTS
 	help
 	  Kunit test for miscdevice API, specially its behavior in respect to