Allow configuration of trailing commas in multi-line signatures (#12975)

Stop outputting trailing commas for C and C++, as it is invalid syntax.

Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>
Co-authored-by: Adam Turner <9087854+aa-turner@users.noreply.github.com>
Co-authored-by: Jakob Lykke Andersen <jakobandersen@users.noreply.github.com>

doc/usage/configuration.rst

@@ -4092,6 +4092,14 @@ Options for the Javascript domain
 
    .. versionadded:: 7.1
 
+.. confval:: javascript_trailing_comma_in_multi_line_signatures
+   :type: :code-py:`bool`
+   :default: :code-py:`True`
+
+   Use a trailing comma in parameter lists spanning multiple lines, if true.
+
+   .. versionadded:: 8.2
+
 
 Options for the Python domain
 -----------------------------
@@ -4181,6 +4189,14 @@ Options for the Python domain
 
    .. versionadded:: 7.1
 
+.. confval:: python_trailing_comma_in_multi_line_signatures
+   :type: :code-py:`bool`
+   :default: :code-py:`True`
+
+   Use a trailing comma in parameter lists spanning multiple lines, if true.
+
+   .. versionadded:: 8.2
+
 .. confval:: python_use_unqualified_type_names
    :type: :code-py:`bool`
    :default: :code-py:`False`