test-execute: cleanup

This makes rename the test units by a consistent naming scheme,
add several logs, and sort internal functions.
No functional change.

test/test-execute/exec-standardinput-data.service

@@ -0,0 +1,19 @@
+[Unit]
+Description=Test for StandardInputText= and StandardInputData=
+
+[Service]
+ExecStart=/bin/sh -x -c 'd=$$(mktemp -d -p /tmp); echo -e "this is a test\nand this is more\nsomething encoded!\nsomething   in multiple lines\nand some more\nand a more bas64 data\nsomething with strange\nembedded\tcharacters\nand something with a exec-stdin-data.service specifier" > $d/text ; cmp $d/text ; rm -rf $d'
+Type=oneshot
+StandardInput=data
+StandardInputText=this is a test
+StandardInputText=and this is more
+StandardInputData=c29tZXRoaW5nIGVuY29kZWQhCg==
+StandardInputText=something \
+ in multiple lines
+StandardInputText=\
+and some more
+StandardInputData=YW5kIGEgbW9y \
+    ZSBiYXM2NCBk\
+YXRhCg==
+StandardInputText=something with strange\nembedded\tcharacters
+StandardInputText=and something with a %n specifier