Changing access control level for few methods in SpanAdapter

[vj4iosdev]

What's changed in this PR?

• Changing the access control level for the below methods from internal to public in SpanAdapter

1. toProtoSpanKind()
2. toProtoSpanEvent()
3. toProtoSpanLink()
4. toStatusProto()

• One minor change in OtlpTraceJsonExporter i,e changing the access control for the method getExportedSpans() to public from internal. I had contributed to this earlier but we were using this file locally. Now we are upgrading to use this directly from this repo.

Why is this change required?

• We are leveraging OpenTelemetry extensively for both mobile and web in our app (nested as well).
  In some of the flows, the WebView generates the Spans and hands over the SpanData to mobile. In this case, the native side, instead of creating new Spans/ids, needs to override the SpanData with the received SpanData (containing already generated span ids.). So we need the above-mentioned methods to be public to do so. Hence opening the PR with the changes required.

[linux-foundation-easycla]

• ✅ login: vj4iosdev (d590b06, d9230d4)
• ❌ The email address for the commit (bdc2693) is not linked to the GitHub account, preventing the EasyCLA check. Consult this Help Article and GitHub Help to resolve. (To view the commit's email address, add .patch at the end of this PR page's URL.) For further assistance with EasyCLA, please submit a support request ticket.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Files	Coverage Δ
...penTelemetryProtocolCommon/trace/SpanAdapter.swift	99.00% <100.00%> (ø)
...etryProtocolGrpc/trace/OtlpTraceJsonExporter.swift	88.57% <100.00%> (ø)

... and 1 file with indirect coverage changes

📢 Thoughts on this report? Let us know!.

[vj4iosdev]

Closing this PR and will open another one due to EasyCLA missing ID commit issue.