Dump stacktrace upon SIGABRT

[yacovm]

This commit makes the node process listen to SIGABRT signal and print its stack trace without terminating.

Why this should be merged

It can be useful to troubleshoot and investigate issues either in production or in development without bringing down the node.

How this works

Using the signal.Notify function, we register to SIGABRT signals and print the stack trace of all goroutines upon a reception of the signal.

How this was tested

I ran the node locally, and issued a SIGABRT signal using kill -SIGABRT.
The node wrote the stack trace of its goroutines without exiting:

[09-06|01:29:48.315] INFO <P Chain> bootstrap/bootstrapper.go:603 fetching blocks {"numFetchedBlocks": 190022, "numTotalBlocks": 17120034, "eta": "15m43s"}
[09-06|01:29:48.715] INFO <P Chain> bootstrap/bootstrapper.go:603 fetching blocks {"numFetchedBlocks": 195011, "numTotalBlocks": 17120034, "eta": "15m53s"}
[09-06|01:29:49.119] INFO <P Chain> bootstrap/bootstrapper.go:603 fetching blocks {"numFetchedBlocks": 200004, "numTotalBlocks": 17120034, "eta": "16m3s"}
[09-06|01:29:49.531] INFO <P Chain> bootstrap/bootstrapper.go:603 fetching blocks {"numFetchedBlocks": 205136, "numTotalBlocks": 17120034, "eta": "16m13s"}
Writing goroutine stack to stderr:
goroutine 484 [running]:
github.com/ava-labs/avalanchego/utils.GetStacktrace(...)
        /Users/yacov.manevich/avalanchego/utils/stacktrace.go:10
github.com/ava-labs/avalanchego/app.Run.func2()
        /Users/yacov.manevich/avalanchego/app/app.go:114 +0xd5
created by github.com/ava-labs/avalanchego/app.Run in goroutine 1
        /Users/yacov.manevich/avalanchego/app/app.go:112 +0x19b

goroutine 1 [semacquire]:
sync.runtime_Semacquire(0xc001d40120?)
        /usr/local/go/src/runtime/sema.go:62 +0x25
sync.(*WaitGroup).Wait(0xc0000061c0?)
        /usr/local/go/src/sync/waitgroup.go:116 +0x48
github.com/ava-labs/avalanchego/app.(*app).ExitCode(0xc0011c5180)
        /Users/yacov.manevich/avalanchego/app/app.go:186 +0x25
github.com/ava-labs/avalanchego/app.Run({0x103fe0000, 0xc0011c5180})
        /Users/yacov.manevich/avalanchego/app/app.go:119 +0x1ab
main.main()
        /Users/yacov.manevich/avalanchego/main/main.go:70 +0x528

goroutine 66 [chan receive]:
…
…
…
net.(*netFD).Read(...)
        /usr/local/go/src/net/fd_posix.go:55
net.(*conn).Read(0xc003b0e048, {0xc005c5c000?, 0x0?, 0xd?})
        /usr/local/go/src/net/net.go:185 +0x48
crypto/tls.(*atLeastReader).Read(0xc00414d448, {0xc005c5c000?, 0x0?, 0xc00414d448?})
        /usr/local/go/src/c[09-06|01:29:50.006] INFO <P Chain> bootstrap/bootstrapper.go:603 fetching blocks {"numFetchedBlocks": 210748, "numTotalBlocks": 17120034, "eta": "16m25s"}
[09-06|01:29:50.307] INFO <P Chain> bootstrap/bootstrapper.go:603 fetching blocks {"numFetchedBlocks": 215063, "numTotalBlocks": 17120034, "eta": "16m28s"}
[09-06|01:29:50.698] INFO <P Chain> bootstrap/bootstrapper.go:603 fetching blocks {"numFetchedBlocks": 220037, "numTotalBlocks": 17120034, "eta": "16m36s"}
[09-06|01:29:51.105] INFO <P Chain> bootstrap/bootstrapper.go:603 fetching blocks {"numFetchedBlocks": 225018, "numTotalBlocks": 17120034, "eta": "16m44s"}
[09-06|01:29:51.501] INFO <P Chain> bootstrap/bootstrapper.go:603 fetching blocks {"numFetchedBlocks": 230031, "numTotalBlocks": 17120034, "eta": "16m51s"}
[09-06|01:29:51.883] INFO <P Chain> bootstrap/bootstrapper.go:603 fetching blocks {"numFetchedBlocks": 235013, "numTotalBlocks": 17120034, "eta": "16m57s"}
[09-06|01:29:52.340] INFO <P Chain> bootstrap/bootstrapper.go:603 fetching blocks {"numFetchedBlocks": 240104, "numTotalBlocks": 17120034, "eta": "17m7s"}
[09-06|01:29:52.704] INFO <P Chain> bootstrap/bootstrapper.go:603 fetching blocks {"numFetchedBlocks": 245208, "numTotalBlocks": 17120034, "eta": "17m10s"}
[09-06|01:29:52.990] INFO <P Chain> bootstrap/bootstrapper.go:603 fetching blocks {"numFetchedBlocks": 250057, "numTotalBlocks": 17120034, "eta": "17m9s"}
[09-06|01:29:53.357] INFO <P Chain> bootstrap/bootstrapper.go:603 fetching blocks {"numFetchedBlocks": 255006, "numTotalBlocks": 17120034, "eta": "17m13s"}