feat: harden encoding/decoding functions against panics

[Stebalien]

Part of libp2p/go-libp2p#1389

These kinds of functions:

1. Handle user input.
2. Often have out-of-bounds, null pointer, etc bugs.
3. Have completely isolated logic where local panics are unlikely to cause memory corruption elsewhere.

[marten-seemann]

As discussed:

• let's keep this to crypto operations
• add stderr output

[marten-seemann]

@Stebalien Can you update this PR to log the stack trace to stderr?

[marten-seemann]

I like the idea, but I don't think recover can be moved to a separate function. I added a random panic to one of the functions and it didn't work.

[Stebalien]

This works:

package main

import (
	"fmt"
)

func myRecover() {
	if err := recover(); err != nil {
		fmt.Println("reccovered: ", err)
	}
}

func foo() {
	defer myRecover()

	panic("foo")
}

func main() {
	foo()
}

I'll see if I can figure out what I did wrong...

[Stebalien]

I've added a test case.