Bor related changes on updated geth

fix: changed geth to bor for docker

This fixes cross-build and mobile framework failures.
It also disables the mac test builder because it was failing
all the time in hard to understand ways and we can't afford
it anymore under Travis CI's new pricing.

* Bit boundary fix for the DAG generation routine

* Fix unnecessary conversion warnings

Co-authored-by: Sergey Pavlov <spavlov@gmail.com>

This new flag downloads a known version of Go and builds with it. This
is meant for environments where we can't easily upgrade the installed Go
version.

* .travis.yml: remove install step for PR test builders

We added this step originally to avoid re-building everything
for every test. go test has become much smarter in recent go
releases, so we no longer need to install anything here.

We decided to move our fuzzing efforts to oss-fuzz since fuzzbuzz is still early access.

- Remove the ws:// prefix from the status endpoint since
  the ws:// is already included in the stack.WSEndpoint().
- Don't register the services again in the node start.
  Registration is already done in the initialization stage.
- Expose admin namespace via websocket.
  This namespace is necessary for connecting the peers via websocket.
- Offer logging relevant options for exec adapter.
  It's really painful to mix all log output in the single console. So
  this PR offers two additional options for exec adapter in this case
  testers can config the log output(e.g. file output) and log level
  for each p2p node.

consensus/ethash: fix the percentage progress report

core/state/snapshot: update generator marker in sync with flushes

travis: drop Go 1.13 builders as it's not supported any more

build: stop building for Ubuntu Eoan, not supported any more

* trie: fix error in stacktrie not committing small roots

* fuzzers: make trie-fuzzer use correct returnvalues

* trie: improved tests

* tests/fuzzers: fuzzer for stacktrie vs regular trie

* test/fuzzers: make stacktrie fuzzer use 32-byte keys

* trie: fix error in stacktrie with small nodes

* trie: add (skipped) testcase for stacktrie

* tests/fuzzers: address review comments for stacktrie fuzzer

* trie: fix docs in stacktrie

build: stop verbose output to keep travis from overflowing

This PR contains a minor optimization in derivesha, by exposing the RLP
int-encoding and making use of it to write integers directly to a
buffer (an RLP integer is known to never require more than 9 bytes
total). rlp.AppendUint64 might be useful in other places too.

The code assumes, just as before, that the hasher (a trie) will copy the
key internally, which it does when doing keybytesToHex(key).

Co-authored-by: Felix Lange <fjl@twurst.com>