fix the exit order of the components of playground

[unbyte]

What problem does this PR solve?

#859

What is changed and how it works?

run components in new process groups so avoid an unexpected exit order

Check List

Tests

• Manual test (add detailed scripts or steps below)

Release notes:

playground: consistent exit order of component processes

[CLAassistant]

All committers have signed the CLA.

[codecov-io]

Codecov Report

Merging #933 (5cde1c9) into master (7d602d5) will decrease coverage by 7.92%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master     #933      +/-   ##
==========================================
- Coverage   55.87%   47.95%   -7.93%     
==========================================
  Files         263      251      -12     
  Lines       19508    19098     -410     
==========================================
- Hits        10901     9158    -1743     
- Misses       6880     8456    +1576     
+ Partials     1727     1484     -243     

Flag	Coverage Δ
cluster	34.99% <ø> (-8.40%)	⬇️
dm	24.28% <ø> (-0.02%)	⬇️
integrate	44.26% <ø> (-5.83%)	⬇️
playground	?
tiup	16.80% <ø> (-0.03%)	⬇️
unittest	23.07% <0.00%> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
components/playground/playground.go	0.00% <0.00%> (-41.17%)	⬇️
components/playground/monitor.go	0.00% <0.00%> (-84.42%)	⬇️
components/playground/command.go	0.00% <0.00%> (-79.60%)	⬇️
components/cluster/command/check.go	6.37% <0.00%> (-72.82%)	⬇️
pkg/cluster/task/limits.go	0.00% <0.00%> (-68.75%)	⬇️
components/playground/grafana.go	10.16% <0.00%> (-66.95%)	⬇️
pkg/cluster/task/sysctl.go	0.00% <0.00%> (-66.67%)	⬇️
components/playground/main.go	4.00% <0.00%> (-65.50%)	⬇️
components/playground/env.go	0.00% <0.00%> (-57.90%)	⬇️
components/cluster/command/audit.go	27.27% <0.00%> (-54.55%)	⬇️
... and 59 more

---

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[unbyte]

[AstroProfundis]

LGTM

[lucklove]

@you06 PTAL

[you06]

LGTM

[ti-srebot]

@you06, Thanks for your review. The bot only counts LGTMs from Reviewers and higher roles, but you're still welcome to leave your comments. See the corresponding SIG page for more information. Related SIG: tiup(slack).

[lucklove]

/lgtm

[lucklove]

/merge

[ti-chi-bot]

Can merge label has been added.

Git tree hash: 3fcbb52

[ti-chi-bot]

@unbyte: Your PR has out-of-dated and I have automatically updated it for you.

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