tests: Move directory redirection test to invocation

This tested #1728, where redirecting a directory (`begin; something;
end < .`) would cause `status` to misbehave.

Unfortunately, on Illumos/OpenIndiana/SunOS, this returns a different
error (EINVAL instead of EISDIR), so we can't check that with our test harness, because
we can't redirect it.

Since it's not important that this gives the same error across
systems (and indeed we provide no way of intercepting the error!),
use an invocation test instead, because that allows different output per-uname.

See #5472.

tests/invocation/directory-redirect.err

@@ -0,0 +1,3 @@
+<W> fish: An error occurred while redirecting file '.'
+open: Is a directory
+RC: 1

tests/invocation/directory-redirect.err.SunOS

@@ -0,0 +1,3 @@
+<W> fish: An error occurred while redirecting file '.'
+open: Invalid argument
+RC: 1

tests/invocation/directory-redirect.invoke

@@ -0,0 +1 @@
+-c 'begin; end > . ; status -b; and echo "status -b returned true after bad redirect on a begin block"'

tests/status.err

@@ -1,5 +1,3 @@
-<W> fish: An error occurred while redirecting file '.'
-open: Is a directory
 status: Invalid combination of options,
 you cannot do both 'is-interactive' and 'is-login' in the same invocation
 status: Invalid combination of options,

tests/status.in

@@ -8,12 +8,6 @@ begin
     or echo '"status -b" unexpectedly returned false inside a begin block'
 end
 
-# Issue #1728
-# Bad file redirection on a block causes `status --is-block` to return 0 forever.
-begin; end >. # . is a directory, it can't be opened for writing
-status -b
-and echo '"status -b" unexpectedly returned true after bad redirect on a begin block'
-
 status -l
 and echo '"status -l" unexpectedly returned true for a non-login shell'