RPC log grouping only tracked whether consecutive messages had the same
transport direction. This made an untimed request appear beneath the
duration header of an unrelated response when both were sent in the same
direction.

Before:

    // Send (took 53.0ms):
    {"jsonrpc":"2.0","id":"##CodeLensRefreshRequest#1226","result":null}
    {"jsonrpc":"2.0","id":53,"method":"textDocument/diagnostic"}

After:

    // Send (took 53.0ms):
    {"jsonrpc":"2.0","id":"##CodeLensRefreshRequest#1226","result":null}

    // Send:
    {"jsonrpc":"2.0","id":53,"method":"textDocument/diagnostic"}

Apply the same boundary handling to received messages while continuing
to group consecutive untimed messages.

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Release Notes:

- N/A or Added/Fixed/Improved ...