cmd: move a few things to starter for easy embedding

[iameli]

What does this pull request do? Explain your changes. (required)
Moves a bit of the node startup functionality from the main package into the starter package to make it easier to boot up the node in an embedded way.

How did you test each of these updates (required)

Node still boots up and runs afteward.

Does this pull request close any open issues?
streamplace/streamplace#69 🙃

Checklist:

• Read the contribution guide
• make runs successfully
• All tests in ./test.sh pass
• README and other documentation updated
• Pending changelog updated

[leszko]

I think it's ok to move it. Thanks for the PR @iameli

Please just check the failing CI. I can also test it in our infra before merging. Thanks!

[codecov]

Codecov Report

❌ Patch coverage is 0% with 178 lines in your changes missing coverage. Please review.
✅ Project coverage is 31.66336%. Comparing base (531a043) to head (772e21f).
⚠️ Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
cmd/livepeer/starter/flags.go	0.00000%	159 Missing ⚠️
cmd/livepeer/starter/starter.go	0.00000%	15 Missing ⚠️
cmd/livepeer/livepeer.go	0.00000%	3 Missing ⚠️
server/mediaserver.go	0.00000%	1 Missing ⚠️

Additional details and impacted files

@@                 Coverage Diff                 @@
##              master       #3700         +/-   ##
===================================================
- Coverage   31.92117%   31.66336%   -0.25781%     
===================================================
  Files            156         157          +1     
  Lines          47445       47446          +1     
===================================================
- Hits           15145       15023        -122     
- Misses         31405       31531        +126     
+ Partials         895         892          -3     

Files with missing lines	Coverage Δ
server/mediaserver.go	67.50381% <0.00000%> (ø)
cmd/livepeer/livepeer.go	0.00000% <0.00000%> (-56.96203%)	⬇️
cmd/livepeer/starter/starter.go	7.21587% <0.00000%> (-0.06568%)	⬇️
cmd/livepeer/starter/flags.go	0.00000% <0.00000%> (ø)

... and 4 files with indirect coverage changes

---

Continue to review full report in Codecov by Sentry.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 531a043...772e21f. Read the comment docs.

Files with missing lines	Coverage Δ
server/mediaserver.go	67.50381% <0.00000%> (ø)
cmd/livepeer/livepeer.go	0.00000% <0.00000%> (-56.96203%)	⬇️
cmd/livepeer/starter/starter.go	7.21587% <0.00000%> (-0.06568%)	⬇️
cmd/livepeer/starter/flags.go	0.00000% <0.00000%> (ø)

... and 4 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[iameli]

@leszko Rebased and fixed the tests, thanks for review! The two GPU builds seem to be failing for this reason, which I recall being a recurring problem we had trouble tracking down:

Run git config --global --add safe.directory '*'
protoc -I=. --go_out=. --go-grpc_out=. net/redeemer.proto
protoc-gen-go-grpc: program not found or is not executable
--go-grpc_out: protoc-gen-go-grpc: Plugin failed with status code 1.
make: *** [Makefile:13: net/redeemer.pb.go] Error 1
Error: Process completed with exit code 2.