compiler/sem*: better lineinfo for templates (#10428)

* compiler/sem*: better lineinfo for templates

Lineinfo for templates is inconsistant across the compiler, for example:

    doAssert true
    ^        ^

    a[int](10)
    ^^    ^

The `^` marks where the compiler thinks the template starts.

For qualified call, we got the same situation with `proc`s before #10427:

    system.once
          ^

Generics lineinfo within template declaration is also incorrect, for
example, this is where the compiler believes the `T` in `[T]` is:

    template a[T](b: T)
                  ^

This PR addresses all of these problems.

* nimsuggest: add tests for template highlighting

nimsuggest/tests/ttemplate_highlight.nim

@@ -0,0 +1,9 @@
+doAssert true#[!]#
+
+discard """
+$nimsuggest --tester $1
+>highlight $1
+highlight;;skTemplate;;1;;0;;8
+highlight;;skTemplate;;1;;0;;8
+highlight;;skEnumField;;1;;9;;4
+"""