Adds timeout to Helm commands.

[alexec]

Checklist:

• Either (a) I've created an enhancement proposal and discussed it with the community, (b) this is a bug fix, or (c) this does not need to be in the release notes.
• The title of the PR states what changed and the related issues number (used for the release note).
• I've updated both the CLI and UI to expose my feature, or I plan to submit a second PR with them.
• Optional. My organization is added to the README.
• I've signed the CLA and my build is green (troubleshooting builds).

[codecov]

Codecov Report

Merging #2570 into master will increase coverage by 0.06%.
The diff coverage is 66.66%.

@@            Coverage Diff            @@
##           master   #2570      +/-   ##
=========================================
+ Coverage   37.93%     38%   +0.06%     
=========================================
  Files         114     114              
  Lines       15866   15867       +1     
=========================================
+ Hits         6019    6030      +11     
+ Misses       9066    9052      -14     
- Partials      781     785       +4

Impacted Files	Coverage Δ
util/helm/client.go	31.19% <0%> (ø)	⬆️
util/helm/cmd.go	34.21% <100%> (+0.58%)	⬆️
util/helm/helm.go	65.75% <100%> (+0.47%)	⬆️
cmd/argocd/commands/login.go	0% <0%> (ø)	⬆️
controller/appcontroller.go	45.7% <0%> (+1.22%)	⬆️

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