Remove checked exceptions from most external APIs

[bitwiseman]

Description

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[bitwiseman]

This going to be a massive issue.

Consumers of this library that expect to be able to detect missing items by catching FileNotFoundException will have to catch UncheckedIOException and then check the type of e.getCause(). That's not so bad per se, but it is a significant change in behavior.

We could handled this by replacing the generic UncheckedIOException with an UncheckedFileNotFoundException, but it would still be a significant change not something that could be used by existing consumers without updates.

[Haarolean]

Is it just one more thing people must consider and adjust when switching from 1.x to 2.x? As a maintainer, I would put a bold notice about all these things in a changelog.