More work on opentelemetry event reporting

Moastly a re-org to avoid new contexts over React component unmounts/
remounts.

src/analytics/OtelPosthogExporter.ts

@@ -1,3 +1,19 @@
+/*
+Copyright 2023 New Vector Ltd
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
 import { SpanExporter } from "@opentelemetry/sdk-trace-base";
 import { ReadableSpan } from "@opentelemetry/sdk-trace-base";
 import { ExportResult, ExportResultCode } from "@opentelemetry/core";