feat(pipes,sockets): allow running scripts in the server's command

[rustatian]

Reason for This PR

closes: https://github.com/spiral/roadrunner/issues/822 closes: #60

Description of Changes

• ✏️ Remove requirement to share the same PID for the worker and root process. According to the fork (and to be precise, fork-exec in go) man pages documentation,

The child inherits copies of the parent's set of open file descriptors.  
Each file descriptor in the child refers to the same open file description (see open(2)) as the corresponding file descriptor in the parent. 
This means that the two file descriptors share open file status flags, file offset, and signal-driven I/O attributes (see the description of F_SETOWN and F_SETSIG in fcntl(2)).

• ✏️ Server plugin can accept scripts (sh, bash, etc) in it's command configuration key:

  server:
  command: "./script.sh OR sh script.sh" <--- UPDATED
  relay: "pipes"
  relay_timeout: "20s"

The script should start a worker as the last command. For the pipes, scripts should not contain programs, which can close stdin, stdout or stderr.

• ✏️ Service plugin now supports env variables passing to the script/executable/binary/any:

  service:
  some_service_1:
  command: "php test_files/loop_env.php"
  process_num: 1
  exec_timeout: 5s # s,m,h (seconds, minutes, hours)
  remain_after_exit: true
  env:  <----------------- NEW
    foo: "BAR"
  restart_sec: 1

License Acceptance

By submitting this pull request, I confirm that my contribution is made under the terms of the MIT license.

PR Checklist

[Author TODO: Meet these criteria.] [Reviewer TODO: Verify that these criteria are met. Request changes if not]

• [x] All commits in this PR are signed (git commit -s).
• [x] The reason for this PR is clearly provided (issue no. or explanation).
• [x] The description of changes is clear and encompassing.
• [x] Any required documentation changes (code and docs) are included in this PR.
• [x] Any user-facing changes are mentioned in CHANGELOG.md.
• [x] All added/changed functionality is tested.

[codecov[bot]]

Codecov Report

:exclamation: No coverage uploaded for pull request base (master@a5b3b2b). Click here to learn what that means. The diff coverage is 60.41%.

@@            Coverage Diff            @@
##             master      #62   +/-   ##
=========================================
  Coverage          ?   68.20%           
=========================================
  Files             ?      112           
  Lines             ?     9314           
  Branches          ?        0           
=========================================
  Hits              ?     6353           
  Misses            ?     2333           
  Partials          ?      628           

Impacted Files	Coverage Δ
memory/memoryjobs/consumer.go	77.50% <0.00%> (ø)
service/config.go	68.75% <ø> (ø)
jobs/listener.go	38.59% <38.59%> (ø)
boltdb/boltjobs/listener.go	58.49% <66.66%> (ø)
server/plugin.go	67.64% <82.35%> (ø)
logger/config.go	75.80% <83.33%> (ø)
amqp/amqpjobs/listener.go	78.57% <100.00%> (ø)
beanstalk/connection.go	59.21% <100.00%> (ø)
beanstalk/listen.go	63.63% <100.00%> (ø)
jobs/plugin.go	63.27% <100.00%> (ø)
... and 7 more

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