reverse_tunnels: integration tests

[basundhara-c]

Description

Commit Message: This PR adds basic integration tests for the reverse tunnels functionality.

Additional Description:

This PR adds integration tests for the reverse tunnel functionality:

1. EndToEndReverseTunnelTest - Tests basic reverse tunnel setup with a single node establishing a connection to a cloud listener, followed by sending HTTP requests through the egress listener that route through the reverse tunnel to a backend service. Validates the complete request/response flow and verifies tunnel statistics.

2. EndToEndReverseTunnelTestWithMutualTLS - Similar to the basic end-to-end test but with mutual TLS (mTLS) between the initiator and responder.

3. ReverseTunnelResiliencyTest - Tests reverse tunnel resilience in a multi-node, multi-cloud scenario. Sets up 2 edge nodes (node-1, node-2) with connections to 2 cloud instances (cloud_1, cloud_2) using LDS. Simulates node-1 failure by removing its initiator listeners via LDS, verifies that node-2 continues to function while node-1 requests fail, then re-adds node-1's listeners and confirms that tunnels are re-established and both nodes become operational again.

Risk Level: Low - Tests only

Testing: New integration tests added

Docs Changes: N/A

Release Notes: N/A

Platform Specific Features: N/A

[repokitteh-read-only]

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Caused by: #42811 was opened by basundhara-c.

see: more, trace.