compiler/types: correctly generates signature for non-proc types (#10658)

This makes signatures generated for nimsuggest correctly distinguish
template/macro/converter from proc.

nimsuggest/tests/tsug_template.nim

@@ -0,0 +1,12 @@
+template tmpa() = discard
+macro tmpb() = discard
+converter tmpc() = discard
+tmp#[!]#
+
+discard """
+$nimsuggest --tester $file
+>sug $1
+sug;;skMacro;;tsug_template.tmpb;;macro (){.noSideEffect, gcsafe, locks: 0.};;$file;;2;;6;;"";;0;;Prefix
+sug;;skConverter;;tsug_template.tmpc;;converter ();;$file;;3;;10;;"";;0;;Prefix
+sug;;skTemplate;;tsug_template.tmpa;;template (): typed;;$file;;1;;9;;"";;0;;Prefix
+"""