Fix ambiguities causing a crash

[s-puig]

Objective

• Disabling some plugins causes a crash due to ambiguities relying in feature flags and not checking if both plugins are enabled causing code like this to crash:

app.add_plugins(DefaultPlugins.build().disable::<AnimationPlugin>())

Solution

• Check if plugins were added before ambiguities.
• Move bevy_gizmos ambiguities from bevy_internal to bevy_gizmos since they already depend on them.

[alice-i-cecile]

#1255 please :( Good fixes though!