config: trim leading/trailing white space priv key

[jchappelow]

It can be difficult to create a text file in many text editors without a trailing newline. To support this, this PR trims leading and trailing whitespace from the contents of the private key file when loading it.

Issue:

Loading config from:  /home/jon/kwil/nodes/n0/config.toml
Loading private key from file:  /home/jon/kwil/nodes/n0/private_key.txt
Error: failed to load genesis and private key: error decoding private key: error decoding private key: encoding/hex: invalid byte: U+000A

[charithabandi]

Interesting find. Wasn't seeing this on my editor.

[jchappelow]

Interesting find. Wasn't seeing this on my editor.

Depends on the editor I guess. nano won't even let me omit the trailing newline, probably being overly pedantic about the definition of a text file