Add encrypted disk storage

[ber4444]

From https://github.com/signalfx/splunk-otel-android/blob/571c5fede657d17382b7b38f2ad69f79df2b7ed0/splunk-otel-android/src/main/java/com/splunk/rum/ZipkinWriteToDiskExporterFactory.java, it seems like you are removing the IP address from logs when using enableDiskBuffering, but no other PII is removed (location etc.), and the logs are stored unencrypted on disk. Can we add an encrypted storage option, since a lot of logs are being lost without this option (we know this for a fact by comparing to other logging solutions which we use in parallel). The lost logs are due to throttling in-memory, e.g. in case of crashes almost nothing is captured.

[breedx-splk]

Thanks @ber4444 this is an interesting and good idea. Because we will be migrating to the OTLP based disk buffering provided by upstream OpenTelemetry, I think that we should work on offering encryption up there.