testsuite: Reduce cut-&-paste in scanltranstree.exp

scanltranstree.exp defines some LTO wrappers around standard
non-LTO scanners.  Four of them are cut-&-paste variants of
one another, so this patch generates them from a single template.
It also does the same for scan-ltrans-tree-dump-times, so that
other *-times scanners can be added easily in future.

The scanners seem to be lightly used.  gcc.dg/ipa/ipa-icf-38.c uses
scan-ltrans-tree-dump{,-not} and libgomp.c/declare-variant-1.c
uses scan-ltrans-tree-dump-{not,times}.  Nothing currently seems
to use scan-ltrans-tree-dump-dem*.

gcc/testsuite/
	* lib/scanltranstree.exp: Redefine the routines using two
	templates.