[v2] Fix multiline natspec comment lexing (#1470)

Fixes #1469 

Goes from matching multiline NatSpec comments with
`r#"/\*\*[^\*]*\*+([^/\*][^\*]*\*+)*/"#` to
`r#"/\*\*([^/\*][^\*]*)?\*+([^/\*][^\*]*\*+)*/"#`.

The main difference is that immediately after the `/**` a character
different than `/` is expected.

A [sourcify run over all the
chains](https://github.com/NomicFoundation/slang/actions/runs/19328166314)
shows a few errors, but I think these are different. Still, a lot less
failing contracts than before.

Author: teofr

crates/solidity-v2/inputs/language/src/definition.rs

@@ -440,7 +440,7 @@ language_v2_macros::compile!(Language(
                             // https://stackoverflow.com/a/36328890
                             scanner = Sequence([
                                 Atom("/**"),
-                                ZeroOrMore(Not(['*'])),
+                                Optional(Sequence([Not(['/', '*']), ZeroOrMore(Not(['*']))])),
                                 OneOrMore(Atom("*")),
                                 ZeroOrMore(Sequence([
                                     Not(['/', '*']),

crates/solidity-v2/outputs/cargo/parser/src/lexer/contexts.generated.rs

@@ -32,12 +32,9 @@ fn multi_line_comment() {
     test(
         "/**/ /**/",
         &[
-            // TODO(v2): lexer is greedy, and tries to match the longest possible token by default.
-            // Grammar should be fixed to consider this input as two separate comments with whitespace in between:
-            // (L::MultiLineComment, 0..4),
-            // (L::Whitespace, 4..5),
-            // (L::MultiLineComment, 5..9),
-            (L::MultiLineNatSpecComment, 0..9),
+            (L::MultiLineComment, 0..4),
+            (L::Whitespace, 4..5),
+            (L::MultiLineComment, 5..9),
         ],
     );