TextField: suffix_icon, prefix_icon and icon can be Control or str

[InesaFitsner]

Description

Properties suffix_icon, prefix_icon and icon now accept both strings (icon name) and Controls.

Fixes #4161

The alignment of suffix and suffix_icon is still different but that's how it is done in Flutter. Now control can be placed into suffix_icon or suffix or both and user can choose which layout better for their app.

Test Code

import flet as ft

def main(page: ft.Page):
       
    txtfield1 = ft.TextField(
        width=400,
        value='Default value',
        #text_size=10,
        icon=ft.icons.ARROW_DROP_DOWN,
        prefix_icon=ft.icons.ARROW_DROP_DOWN,
        prefix = ft.Icon(ft.icons.ARROW_DROP_DOWN),
        bgcolor=ft.colors.AMBER_100,
        text_vertical_align=ft.VerticalAlignment.CENTER,
        suffix_icon = ft.icons.ARROW_DROP_DOWN,
        suffix = ft.Icon(ft.icons.ARROW_DROP_DOWN),
    )

    txtfield2 = ft.TextField(
        width=400,
        value='Default value',
        #text_size=10,
        icon=ft.Container(bgcolor=ft.colors.RED, height=10, width=10),
        prefix_icon=ft.Container(bgcolor=ft.colors.RED, height=10, width=10),
        prefix = ft.Container(bgcolor=ft.colors.RED, height=10, width=10),
        bgcolor=ft.colors.AMBER_100,
        text_vertical_align=ft.VerticalAlignment.CENTER,
        suffix_icon = ft.Container(bgcolor=ft.colors.RED, height=10, width=10),
        suffix = ft.Container(bgcolor=ft.colors.RED, height=10, width=10),
    )


    page.add(ft.Row([txtfield1, txtfield2]))

ft.app(target=main)

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist:

• I signed the CLA.
• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings

• New and existing tests pass locally with my changes
• I have made corresponding changes to the documentation (if applicable)

Screenshots (if applicable):

Additional details

[FeodorFitsner]

Do we need to add that to Dropdown and other controls using buildInputDecoration()?

[ndonkoHenri]

@sourcery-ai review