Replace *Escape with *EscapeList

Follow the change to blueprint to make *Escape take and return a string
and add *EscapeList that take and return slices of strings.  Fix up
a few places that were unnecessarily converting a string to a slice
and back to a string.

Test: m nothing
Change-Id: I3fa87de175522205f36544ef76aa2f04aef1b936

cc/tidy.go

@@ -69,7 +69,7 @@ func (tidy *tidyFeature) flags(ctx ModuleContext, flags Flags) Flags {
 	if len(withTidyFlags) > 0 {
 		flags.TidyFlags = append(flags.TidyFlags, withTidyFlags)
 	}
-	esc := proptools.NinjaAndShellEscape
+	esc := proptools.NinjaAndShellEscapeList
 	flags.TidyFlags = append(flags.TidyFlags, esc(tidy.Properties.Tidy_flags)...)
 	// If TidyFlags is empty, add default header filter.
 	if len(flags.TidyFlags) == 0 {