patch 9.0.0564: a few tests keep failing on MacOS M1

Problem:    A few tests keep failing on MacOS M1.
Solution:   Add a test check CheckNotMacM1.  Fix timer tests.
diff --git a/src/testdir/check.vim b/src/testdir/check.vim
index c4dca0b..c3f2563 100644
--- a/src/testdir/check.vim
+++ b/src/testdir/check.vim
@@ -111,6 +111,14 @@
   endif
 endfunc
 
+" Command to check for not running on a MacOS M1 system.
+command CheckNotMacM1 call CheckNotMacM1()
+func CheckNotMacM1()
+  if has('mac') && system('uname -a') =~ '\<arm64\>'
+    throw 'Skipped: does not work on MacOS M1'
+  endif
+endfunc
+
 " Command to check that making screendumps is supported.
 " Caller must source screendump.vim
 command CheckScreendump call CheckScreendump()