examples: minimize use of raw base32 in examples

[marceline-cramer]

Description

I noticed that in the example code (particularly iroh-net's code), there are a few explicit uses of base32 encoding and decoding that are unnecessary. In particular, SecretKey is manually base32-encoded in the networking examples, although the Display implementation uses that same encoding. I figure that the examples were just written before the utility encoding/decoding code in the main libraries were and weren't updated when that utility code was added. I hope that catching this is helpful!

Breaking Changes

None.

Notes & open questions

None.

Change checklist

• Self-review.
• Documentation updates if relevant.
• Tests if relevant.
• All breaking changes documented.

[dignifiedquire]

thanks a lot, those examples were probably written before we had all these niceties :)