Allow the color and bgcolor of FilledButton and FilledTonalButton to be set through the style

[ndonkoHenri]

Closes #2268

Test code:

import flet as ft


def main(page: ft.Page):
    page.window_always_on_top = True
    page.theme_mode = ft.ThemeMode.LIGHT

    page.add(
        ft.FilledButton(
            "Material",
            icon=ft.icons.ACCESSIBILITY,
            style=ft.ButtonStyle(bgcolor=ft.colors.GREEN, color=ft.colors.BLUE_ACCENT),
        ),
        ft.FilledTonalButton(
            "Material",
            icon=ft.icons.ACCESSIBILITY,
            style=ft.ButtonStyle(bgcolor=ft.colors.RED, color=ft.colors.YELLOW),
        ),
    )


ft.app(target=main)