TOX-3117 bugfix -c pyproject with non legacy

Running tox -c pyproject.toml with content not ini legacy end up with a failure:
could not recognize config file pyproject.toml

docs/changelog/3117.bugfix.rst

@@ -0,0 +1 @@
+multiple source_type supports for the same filename. Like pyproject.toml can be load by both TomlPyProject & LegacyToml

src/tox/config/source/discover.py

@@ -68,8 +68,8 @@ def _locate_source() -> Source | None:
 
 def _load_exact_source(config_file: Path) -> Source:
     # if the filename matches to the letter some config file name do not fallback to other source types
-    exact_match = next((s for s in SOURCE_TYPES if config_file.name == s.FILENAME), None)  # pragma: no cover
-    for src_type in (exact_match,) if exact_match is not None else SOURCE_TYPES:  # pragma: no branch
+    exact_match = list(s for s in SOURCE_TYPES if config_file.name == s.FILENAME)  # pragma: no cover
+    for src_type in exact_match or SOURCE_TYPES:  # pragma: no branch
         try:
             return src_type(config_file)
         except ValueError:  # noqa: PERF203