Automated test for parachain disconnection

[Kailai-Wang]

Context

We'd need an automated test to test the reconnection of tee-worker when parachain goes down.

1. parachain disconnects (e.g. gets killed)
2. tee-worker stops
3. restarts parachain
4. restarts tee-worker => it should continue

I manually tested it several times, and it looked good, but it would be great if we could have an automated test.

Here's the log of TEE-worker when the connection to parachain was lost:

[2023-04-15T19:51:35Z ERROR integritee_service] Parentchain block syncing terminated with a failure: ApiSubscriptionDisconnected(RecvError)
[!] Parentchain block syncing has terminated
[2023-04-15T19:51:36Z DEBUG enclave_runtime::top_pool_execution] ----------------------------------------
[2023-04-15T19:51:36Z DEBUG enclave_runtime::top_pool_execution] Start sidechain block production cycle
[2023-04-15T19:51:36Z DEBUG its_consensus_common::block_import] Attempting to import sidechain block (number: 94, hash: 0xa5b4cad4b53f0c7d6a66abf697fdefe15b406f5108ea9790e7e2d363cfcc18f6, parentchain hash: 0x620f21ccdda42f71a5682bdc054a908657c7d0c5db491470ce461f1b5133f01b)
[2023-04-15T19:51:36Z ERROR ws::handler] WS Error <Io(Os { code: 111, kind: ConnectionRefused, message: "Connection refused" })>

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