Fix CPANTS test failures

Case 116001: Fix CPANTS test failures with the following changes:

    * Modify Filesys::POSIX::Userland::Tar's $fs->tar() method option
      'ignore_missing' to test $! for ENOENT rather than checking $@,
      which can get localized to something other than what we used to
      expect

    * Modify t/tar-missing.t to use Test::Filesys::POSIX::Error function
      throws_errno_ok()

    * Modify Test::Filesys::POSIX::Error to use Try::Tiny, rather than
      plain block eval(), which causes issues with Perl <=5.12

    * Modify Test::Filesys::POSIX::Error to build a default number=>name
      cache populated with number=>number, in case of an incompatible
      Errno module