🔧 Allow negating --showlocals with --no-showlocals

This is necessary for addopts=--showlocals where individual test runs
need to not show locals.

src/_pytest/terminal.py

@@ -178,6 +178,13 @@ def pytest_addoption(parser: Parser) -> None:
         default=False,
         help="Show locals in tracebacks (disabled by default)",
     )
+    group._addoption(
+        "--no-showlocals",
+        action="store_false",
+        dest="showlocals",
+        default=True,
+        help="Show locals in tracebacks (disabled by default)",
+    )
     group._addoption(
         "--tb",
         metavar="style",