Rewrite with_history test helper to be more robust

Write mock history to a temp file and load it directly with `fc -R`
instead of running each command individually to build up the history.

spec/multi_line_spec.rb

@@ -1,11 +1,6 @@
 describe 'a multi-line suggestion' do
   it 'should be displayed on multiple lines' do
-    with_history(-> {
-      session.send_string('echo "')
-      session.send_keys('enter')
-      session.send_string('"')
-      session.send_keys('enter')
-    }) do
+    with_history("echo \"\n\"") do
       session.send_keys('e')
       wait_for { session.content }.to eq("echo \"\n\"")
     end