Set panic as default fallible system param behavior

[MiniaczQ]

Objective

Fixes: #16578

Solution

This is a patch fix, proper fix requires a breaking change.

Added Panic enum variant and using is as the system meta default.
Warn once behavior can be enabled same way disabling panic (originally disabling wans) is.

To fix an issue with the current architecture, where all combinator system params get checked together,
combinator systems only check params of the first system.
This will result in old, panicking behavior on subsequent systems and will be fixed in 0.16.

Testing

Ran unit tests and fallible_params example.

[MiniaczQ]

Naive approach comes with some issues, I'm not sure when I'll have time to truly sit down and work on this, so feel free to take over as needed

[alice-i-cecile]

Can you say a bit more about the issues you encountered?

[MiniaczQ]

The main issue is stuff that was fixed in the System::run() -> Option<S::Out> rework (didn't land in 0.15).
In a combination system, like a.and(b) or a.pipe(b) we're running param checks for all systems before running any of them.
This results in resource_exists::<MyRes>.and(do_stuff) failing params, because do_stuff doesn't have MyRes even though it wouldn't run because of failed condition.
When we change default fail behavior to panic, this causes crashes.

I've had time to think about it since this PR.
We didn't ship a complete feature, so I think we should be fine to downscope it.
Since combination systems are incomplete, let's just ensure the first system (or the system, if no combinations are used) works correctly with fallible params, do not check params for subsequent ones and just let app crash like it did in 0.14.
In 0.16 we can ship the correct param checking behavior, where we do it directly before running a system.

[alice-i-cecile]

I'm okay with that as the behavior for now :)

[MiniaczQ]

As agreed, this is no longer supported in this scope