feat(cli): Add kill subcommand

[irvinlim]

Closes #82.

[codecov]

Codecov Report

Merging #84 (e245a0f) into main (8320441) will increase coverage by 0.07%.
The diff coverage is 73.26%.

@@            Coverage Diff             @@
##             main      #84      +/-   ##
==========================================
+ Coverage   62.79%   62.87%   +0.07%     
==========================================
  Files         199      200       +1     
  Lines       10340    10434      +94     
==========================================
+ Hits         6493     6560      +67     
- Misses       3499     3517      +18     
- Partials      348      357       +9     

Impacted Files	Coverage Δ
pkg/cli/formatter/time.go	82.35% <50.00%> (-17.65%)	⬇️
pkg/cli/cmd/cmd_kill.go	69.23% <69.23%> (ø)
pkg/cli/cmd/cmd.go	92.30% <100.00%> (+0.20%)	⬆️
pkg/cli/cmd/cmd_get_job.go	79.19% <100.00%> (ø)
pkg/cli/cmd/cmd_get_jobconfig.go	72.95% <100.00%> (ø)
pkg/cli/cmd/cmd_list_job.go	82.10% <100.00%> (ø)
pkg/cli/cmd/cmd_list_jobconfig.go	86.04% <100.00%> (ø)
pkg/cli/cmd/cmd_run.go	76.47% <100.00%> (ø)
pkg/runtime/testing/command.go	77.50% <100.00%> (+2.15%)	⬆️
pkg/runtime/testing/reconciler.go	74.41% <100.00%> (+0.60%)	⬆️

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