Replace unwrap calls with expect in bevy_sprite crate

[mnmaita]

Objective

• Addresses Tracking issue: Replace unwrap with expect #3899 for bevy_sprite crate.

Solution

• Replaced all unwrap calls with expect calls and added comprehensive error messages when these statements panic.

Feel free to review the error messages and provide suggestions on how they could be made clearer.

[mnmaita]

Should I use the following pattern (suggested by clippy) on places where I call a format! macro as the argument for the expect call?

foobar.unwrap_or_else(|_| panic!(/* ... */))

[mnmaita]

Also, I was trying to display HandleIds as part of some errors but noticed it's an enum with tuple variants and it doesn't implement Debug, so any suggestion on how to clarify messages on loops or places where a hint on the entity/handle/etc. could be useful is more than welcome.

[james7132]

Should I use the following pattern (suggested by clippy) on places where I call a format! macro as the argument for the expect call?

foobar.unwrap_or_else(|_| panic!(/* ... */))

Please do, otherwise there will be a String allocated even when there isn't an error.

[alice-i-cecile]

Closing per discussion in #3899 <3