test: E2E tests against ipfs-webui HEAD

[lidel]

Parent: ipfs/ipfs-webui#1164

This PR adds CircleCI config for running ipfs-webui's end to end tests against ipfs binary produced by this repo.

It does not increase CI time, as its runs in parallel to interop tests, and those take much longer:

The goal is to catch regressions in go-ipfs+ipfs-webui interop, such as this one (hardened go-ipfs was unable to connect to peer that used weak key size):

When everything works as expected, it looks like this:

TODO

• use custom executor capable of running Chrome in headless mode
• fix ipfsd-ctl error with latest go-ipfs master
  • error: [test:e2e ] SyntaxError: Unexpected end of JSON input
  • reason: ipfs init failed because ipfsd-ctl uses 1024 bit keys in test mode
  • fix: set LIBP2P_ALLOW_WEAK_RSA_KEYS: true in test env
• confirm version from IPFS_GO_EXEC is used
  • confirmed: [test:e2e ] E2E using /go-ipfs/0.5.0-dev/28a9a6501 (/tmp/circleci-workspace/bin/ipfs) with Peer ID QmXcHQoM2SFTAaxE2khR4WpPDCnouYNMPPEkqxZxKNk6oa
• confirm CI works and added time is acceptable
  • we should be good: it takes ~6m and finishes long before interop tests suite (both run in parallel)
• consider: if test time is low enough, run original tests first to confirm ipfs-webui's HEAD is green, then run again with ipfs from this repo's HEAD
  • decision: running tests second time take less than a minute, sounds feasible
  • note: if upstream tests fail, we dont break the build, but exit with code 0 (skipping, as there is no way to test for regression if upstream webui is broken)
• fix failed to negotiate security protocol: MAC verification failed)
  • note: it is super cool that the moment we've set up E2E regression test, we've found a regression 👌
  • reason: LIBP2P_ALLOW_WEAK_RSA_KEYS=true did not decrease minimal key size limit everywhere
  • fix: changing to LIBP2P_ALLOW_WEAK_RSA_KEYS=1 fixed the "MAC verification failed" error. I updated true → 1 everywhere.
• switch to ipfs-webui's master
  • remove checkout of "fix/test-external" (requires fix: build before e2e and run it on random port ipfs-webui#1377 to land first)

[lidel]

@Stebalien this is ready for review

[Stebalien]

🎉