e2e: Print process IDs for debugging.

[prestonvanloon]

What type of PR is this?

Other

What does this PR do? Why is it needed?

How to attach a debugger to an e2e subprocess. For example, it may be useful to debug and break the beacon chain process.

# Build and execute the endtoend test with -c dbg to compile with debugging symbols and --spawn_strategy=standalone to disable bazel sandboxing.
bazel test //testing/endtoend:go_default_test  --test_output=streamed --test_arg=-test.v --spawn_strategy=standalone -c dbg

When the test runs, you will see a log message like this:

    component_handler_test.go:238: This test PID: 272686 (parent=272671)
        Beacon chain nodes: [274706 274705]
        Validators: [274733 274734]
        ETH1 nodes: [274691]

This log prints the process ID's spawned by this test. A remote debugger, dlv, can attach to process 274706 as such:

dlv --listen=:2345 --headless=true --api-version=2 attach 274706

And then a remote debugger can interact with dlv on port 2345.

Which issues(s) does this PR fix?

Other notes for review

Note: I had to tackle this error message

Could not attach to pid 274706: this could be caused by a kernel security setting, try writing "0" to /proc/sys/kernel/yama/ptrace_scope 

The solution was echo 0 > /proc/sys/kernel/yama/ptrace_scope

My goland config looked like

[nisdas]

This will be great for debugging