debug/dwarf: better stmt list attr checking in LineReader

debug/dwarf: better stmt list attr checking in LineReader

Check for insane statement list attribute values when
constructing LineReader's for a compilation unit.

Fixes #52354.

Change-Id: Icb5298db31f6c5fe34c44e0ed4fe277a7cd676b9
Reviewed-on: https://go-review.googlesource.com/c/go/+/400255
Run-TryBot: Than McIntosh <thanm@google.com>
Auto-Submit: Than McIntosh <thanm@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>