[nimsuggest] fix def call on identifier 2 times on the line (#20228)

- apparently TLineInfo's implementation of `==` ignores the column. After I fixed
the code to use exact TLineInfo comparison I fixed several other issues hidden
by that issue.

- Replaced `tuple[sym, info]` with `SymInfoPair`

nimsuggest/tests/tv3.nim

@@ -7,6 +7,8 @@ type
 proc test(f: Foo) =
   echo f.ba#[!]#r
 
+#[!]#
+
 discard """
 $nimsuggest --v3 --tester $file
 >use $1
@@ -22,4 +24,8 @@ outline	skProc	tv3.test	proc (f: Foo){.gcsafe, locks: 0.}	$file	7	5	""	100
 sug	skField	bar	string	$file	5	4	""	100	Prefix
 >globalSymbols test
 def	skProc	tv3.test	proc (f: Foo){.gcsafe, locks: 0.}	$file	7	5	""	100
+>globalSymbols Foo
+def	skType	tv3.Foo	Foo	$file	4	2	""	100
+>def $2
+>use $2
 """

nimsuggest/tests/tv3_definition.nim

@@ -0,0 +1,9 @@
+
+let foo = 30
+let bar = foo + fo#[!]#o + foo
+
+discard """
+$nimsuggest --v3 --tester $file
+>def $1
+def	skLet	tv3_definition.foo	int	$file	2	4	""	100
+"""