move examples into rustic_core crate

[aawsome]

Instead of having an own crate for each example, this PR moves all examples into the rustic_core crate. This simplifies the workspace and makes the examples available in the distributed rustic_core crate.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 42.5%. Comparing base (64d052d) to head (85e78e2).

Additional details and impacted files

see 26 files with indirect coverage changes

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