Add more configuration options to fps overlay

[afonsolage]

Objective

• Describe the objective or issue this PR addresses.
• Closes Allow users to customise the colors of FrameTimeGraph #21305
• Closes FPS overlay: Allow users to specify positioning #21017
• Fixes The frame time graph enabling is *weird* #21201

Solution

• Added FpsOverlayPositionConfig into FpsOverlayConfig to enable fine configuration of overlay root node position.
• Added min_color and max_color to FrameTimeGraphConfig to enable frame graph color configuration.
• Moved text config to FpsOverlayTextConfig to enable/disable only the text part of overlay.
• Added an "overlay-wise" enable option which would disable the entire overlay,

This PR is kinda blocked by #21022, since there is an intent to convert the fps overlay to use bevy_sprite, but I decided to do it anyways because I don't think the benefits of converting fps_overlay to bevy_sprite worth it.

The fix for #21021 may not be ideal, since it can be confusing to have 3 enable options on a simple component like fps_overlay, but I think it would be nice to be able to only use the graph of the overlay, without the text itself:

Testing

• I used the fps_overlay example as testing and its working fine.

[Zeophlite]

In terms of enabled , I suggest rename

• in FrameTimeGraphConfig change enabled to graph_enabled
• in FpsOverlayTextConfig change enabled to text_enabled

And then for FpsOverlayConfig remove enabled and replace any usage with frame_time_graph_config.graph_enabled || text_config.text_enabled

[Zeophlite]

Might as well rename frame_time_graph_config to graph_config

[afonsolage]

The problem with removing enabled from FpsOverlayConfig is that if the user wanna hide the overlay, like using some toggle key, it needs to work with two nested enabled properties, like described in #21201. Ideally to hide/show there should be only one property config for the entire overlay.

I'm ok with the other suggestions.

[jf908]

Maybe set_enabled(bool) could be a method that sets both text_enabled and graph_enabled?

[afonsolage]

This still keeps the problem of "verbosity", because Bevy uses a lot of "declaration config". Imagine that I wanna it disabled so I can enable it with hotkey later on:

app.add_plugins(FpsOverlayPlugin {
    config: FpsOverlayConfig {
       text_config: FpsOverlayTextConfig {
           enabled: false,
           ..default()
       },
       frame_time_graph_config: FrameTimeGraphConfig {
            enabled: false,
            ..default()
        },
        ..default()
    },
});

vs

app.add_plugins(FpsOverlayPlugin {
    config: FpsOverlayConfig {
       enabled: false,
        ..default()
    },
});