test: Rename test directories to use an explicit order

For convenience, rename the directories so the order is explicit in the name.
Make the simple test run first, to save time if it's not working.

test/t-02-exim/msmtprc

@@ -0,0 +1,14 @@
+account default
+
+host srv-chasquid
+port 1025
+
+tls on
+tls_trust_file config/domains/srv-chasquid/cert.pem
+
+from user@srv-chasquid
+
+auth on
+user user@srv-chasquid
+password secretpassword
+