tests: Disable some slow tests under ASAN

These take over two minutes under ASAN (like ~40 seconds without, so
they aren't quick to begin with), and don't really give any additional
insight.

So we skip them to save time

tests/checks/check-all-fish-files.fish

@@ -1,4 +1,6 @@
 #RUN: %fish -C 'set -l fish %fish' %s
+# disable on CI ASAN because it's suuuper slow
+#REQUIRES: test -z "$FISH_CI_SAN"
 # Test ALL THE FISH FILES
 # in share/, that is - the tests are exempt because they contain syntax errors, on purpose
 

tests/checks/check-completions.fish

@@ -1,4 +1,6 @@
 #RUN: %fish -C 'set -l fish %fish' %s
+# disable on CI ASAN because it's suuuper slow
+#REQUIRES: test -z "$FISH_CI_SAN"
 # Test all completions where the command exists
 
 # No output is good output