Icons - add support for custom icons

Is this a new component or an extension of an existing one?
What is the existing component, if any?

Existing, MenuToggle, ToolbarFilter

When using PF tokens to create a custom theme, MenuToggle and ToolbarFilter use default icons in PF that currently cannot be changed via a prop since the prop does not exist, while components like Label, Alert, and Button, offer this functionality.

An alternative option was discussed at today's working session (cc @mcoker), which would include adding support for custom icons directly to react-icons and then importing any custom overrides.

Related: https://github.com/patternfly/patternfly-react/issues/10634

Describe the feature
A clear and concise description of the new feature. What is the expected behavior?

Are there visuals for this feature? If applicable, please include examples for each state and for varying widths

See below. MUI uses a different toggle icon for their menu toggle.

Include screenshots or links to Marvel or other mockups.
MUI:

PF:

Any other information?
Would it be possible to prioritize this work for an upcoming sprint to align with RHOAI priorities for the MUI theming effort @nicolethoen ?

まず MenuToggle と ToolbarFilter コンポーネントの実装を確認し、次に issue #10634 と react-icons の拡張に関する議論を読んでください。ユーザーが合意済みで文書化された API を通じて両方のコンポーネントにカスタムアイコンを指定でき、Label、Alert、Button に既存のアイコン対応と一貫した動作になることが完了の条件です。