Add e2e test for context propagation

[edeNFed]

Currently, each e2e test checks a single instrumented library.
We are missing an e2e test that validates that context propagation works.

An example of this kind of test:

• Start two applications: gRPC client and server
• instrument both
• Validate that both spans contains the same trace id

Note that there are two kinds of context propagation that we should validate:

• In-process (for example: HTTP server that performs grpc requests to other servers)
• cross-process (like the example described above)