Improving DotLottie error handling

[mkj-is]

We faced some issues related to failing animation loads using async DotLottie methods (#1956).

I figured error handling in DotLottie loading can be improved in some ways:

• Using LottieLogger to report any errors which are silent.
• Return internal error as part of handleResult (DotLottieError.invalidData is too generic for debugging purposes and will be returned even in case there was some issue with opening/decompressing .lottie file or manifest).

Places where error reporting can be improved:

• https://github.com/airbnb/lottie-ios/blob/master/Sources/Public/DotLottie/DotLottieFile.swift#L45
• https://github.com/airbnb/lottie-ios/blob/master/Sources/Public/DotLottie/DotLottieFile.swift#L128
• https://github.com/airbnb/lottie-ios/blob/master/Sources/Public/DotLottie/DotLottieFileHelpers.swift#L245

Do you think it would be better to send errors to LottieLogger or return them in handleResult closure?

I am willing to help with the implementation.

[calda]

I think it would make sense to log these errors as either LottieLoggier.shared.assertionFailure or LottieLogger.shared.warn.

[calda]

It would also be nice to add context about the underlying error to the various DotLottieError cases.

[mkj-is]

Great, I will open a draft PR on which we can iterate.

[mkj-is]

Opened a PR: #1969

I am not wrapping the underlying errors since public loading methods return the generic Error.

It actually made the code shorter and I was able to get rid of some unused helper variables.