HarfRust should not panic on an invalid language

[drott]

From Blink testing with HB-HR:

STDERR: [9524:11572:0529/031140.483:FATAL:third_party/harfbuzz/src/src/rust\shape.rs:188] panicked at ../../third_party/harfbuzz/src/src/rust\shape.rs:188:53:
STDERR: called `Result::unwrap()` on an `Err` value: "invalid language"

For a library, I don't think we should panic on an invalid language here, but instead ignore it or assume a default.

[behdad]

I suggest hb-hr to call from_bytes instead. Would that fix this issue?

[behdad]

Would need making from_bytes public. And will avoid str roundtrip since internal storage is vector of bytes anyway.

[drott]

+1 for from_bytes being public - that was part of the experimental local patches I had for moving Language processing to being bytes based and not using from_utf8 anywhere.