fix: Open a new connection on each stream reconnect

[kinyoklion]

Summary

After a stream read timeout on an HTTP/2 connection, OkHttp keeps the connection in the pool and treats it as healthy until a 1 second ping deadline passes. After a long-lived stream fails, the first reconnect comes 0.5 to 1 second later. So when the network silently drops the stream connection, the reconnect opens a new stream on the same dead connection and waits for another 5 minute read timeout. Recovery takes about 10 minutes instead of 5.

The stream's OkHttp client now uses a connection pool that keeps no idle connections, so each reconnect opens a new connection. This applies to the FDv1 streaming data source and the FDv2 streaming synchronizer. The stream client has its own pool, so polling and event delivery are unchanged.

This also updates okhttp-eventsource to 5.0.1, which closes the response body when a stream stops (launchdarkly/okhttp-eventsource#114). Without that, a restart that the SDK starts itself, such as after an FDv2 goodbye or invalid data, leaves the abandoned HTTP/2 call holding the old connection, so this pool setting cannot close it.

New tests count TCP connections across a reconnect and fail without this change.

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Note

Overview
Fixes slow recovery when an SSE stream dies on HTTP/2 by forcing each stream reconnect to use a fresh TCP connection instead of reusing a pooled connection OkHttp may still treat as healthy for ~1s after a read timeout.

StreamProcessor (FDv1) and StreamingSynchronizerImpl (FDv2) now configure the eventsource OkHttp client with ConnectionPool(0, 1, SECONDS) after httpProperties applies its default pool, so idle connections are not kept for streaming only. Polling and other HTTP clients are unchanged.

Bumps okhttp-eventsource to 5.0.1 (pairs with upstream fix for abandoned HTTP/2 calls on SDK-initiated restarts). Adds integration tests that count TCP connections across a reconnect and expect two connections.

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[kinyoklion]

I'll hold the release of this one until the updated event source is included as well.