Make enums ser/deser forward-compatible

[romtsn]

Description

Some enums like

sentry-java/sentry/src/main/java/io/sentry/SpanStatus.java

Line 119 in 7300956

return SpanStatus.valueOf(reader.nextString().toUpperCase(Locale.ROOT));

ser/deser are not forward compatible, meaning if, for example, RN adds a new span status, the deserialization will fail during serialization roundtrip.

We should fallback to UNKNOWN statuses/enums in case the value is not part of the enum set.

[marandaneto]

I'd not say that we should always fallback to UNKNOWN statues/enums, that's fine if this value is only used at runtime for ifs, switches, etc, but if the value is forwarded to Sentry, its value should be kept.
Eg. If RN or Flutter captures a transaction with a status that is not defined in the SpanStatus enum, this value should not be lost during roundtrip serialization.
This is a real example getsentry/develop#383 gets implemented.

[kahest]

closing as outdated - if it's still relevant it will come up again