runtime: fix output for bad pcHeader
runtime: fix output for bad pcHeader

With print, the output all runs together.
Take this opportunity to clean up and label all the fields.
Print pluginpath unilaterally; no reason not to.
Wrap long lines. Remove pointless newline from throw.

Change-Id: I37af15dc8fcb3dbdbc6da8bbea2c0ceaf7b5b889
Reviewed-on: https://go-review.googlesource.com/c/go/+/350734
Trust: Josh Bleecher Snyder <cdc248cc4d32e4fbfe04e45228163bcecd48a0b9@gmail.com>
Run-TryBot: Josh Bleecher Snyder <cdc248cc4d32e4fbfe04e45228163bcecd48a0b9@gmail.com>
TryBot-Result: Go Bot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Cherry Mui <d62e63aa42ce272d7b6a5055d97e942b33a34679@google.com>

cloudflare/go,CAFxX/go,CAFxX/go,CAFxX/go,nawawi/go,CAFxX/go,cloudflare/go,CAFxX/go,nawawi/go,golang/go,golang/go,nawawi/go,golang/go,cloudflare/go,cloudflare/go,cloudflare/go,golang/go,nawawi/go,nawawi/go,golang/go,cloudflare/go,nawawi/go,nawawi/go,cloudflare/go,CAFxX/go,nawawi/go,cloudflare/go,golang/go,golang/go,golang/go,CAFxX/go,CAFxX/go