Strengthen Linux kernel capabilities detection

• Add CONFIG_BLOCK Linux config requirement to ZFS_AC_KERNEL_CONFIG_DEFINED. OpenZFS won't compile without that block device support due to large amount of functional dependencies on it.

• Remove dependency on groups_alloc() in ZFS_AC_KERNEL_SRC_GROUP_INFO_GID to circumvent the missing stub in Linux 4.X kernel headers.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: szubersk <szuberskidamian@gmail.com>
Closes #13351