Read lines with default encoding from os

[breedx-splk]

Repeat of #12419 which fixes #12418

@laurit had previously asked if a file could be provided to reproduce this. Unfortunately, it's problematic because it depends on the os encoding. The original problem was from z/OS.....which I have no reasonable way of reproducing with tests etc. It's odd that z/os wouldn't support or use UTF-8, but here we are.

This change should at least handle those edge cases.

[laurit]

To me using Charset.defaultCharset() doesn't seem like the best option. Since jdk18 the default charset is utf-8 unless user explicitly configures to use a different encoding, see https://openjdk.org/jeps/400. On older jdks users could use -Dfile.encoding=utf-8 even if the system encoding is something different.
Looking at https://github.com/moby/sys/blob/mountinfo/v0.7.2/mountinfo/mountinfo_linux.go#L23 I think they are also reading it as utf-8, could be wrong, don't really know any go. Without a sample that doesn't decode as with utf-8 it is hard to guess why it would fail. Could be that z/os does something weird. Also could be that the assumption of this file containing utf-8 is wrong and only works because everybody uses utf-8. Weren't paths just blobs from the linux kernel perspective? Instead of Charset.defaultCharset() I'd try StandardCharsets.ISO_8859_1. From what I understand we don't really care about the paths or whatever that could be in utf-8, container id is a hex string and the other symbols we use for parsing are all present in iso-8859-1.