fix(dashboard): Cleanup viewcontroller after each request. Fixes #2095

[unrolled]

Fixes: #2095

Every time GetRolloutInfo route is called it creates a new RolloutViewController, but the context passed into the view controller was never cancelled. This resulted in the informers never being cleaned up which manifested as a memory leak. Cancelling the view controllers context after the request has processed eliminates the "memory leak".

The graph below shows our production instance (pod named argo-rollouts-dashboard-8dfdc4bd6-vkhkp) vs the test instance with the fix applied (pod named argo-rollouts-dashtest). Both instances were receiving API requests every 15seconds.

Checklist:

• Either (a) I've created an enhancement proposal and discussed it with the community, (b) this is a bug fix, or (c) this is a chore.
• The title of the PR is (a) conventional with a list of types and scopes found here, (b) states what changed, and (c) suffixes the related issues number. E.g. "fix(controller): Updates such and such. Fixes #1234".
• I've signed my commits with DCO
• I have written unit and/or e2e tests for my change. PRs without these are unlikely to be merged.
• My builds are green. Try syncing with master if they are not.
• My organization is added to USERS.md.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 4 lines in your changes missing coverage. Please review.

Project coverage is 82.71%. Comparing base (5f59344) to head (6ff6e56).
Report is 4 commits behind head on master.

Files with missing lines	Patch %	Lines
server/server.go	0.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3966      +/-   ##
==========================================
+ Coverage   82.69%   82.71%   +0.01%     
==========================================
  Files         163      163              
  Lines       22895    22898       +3     
==========================================
+ Hits        18934    18940       +6     
+ Misses       3087     3086       -1     
+ Partials      874      872       -2     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[github-actions]

Published E2E Test Results

  4 files    4 suites   3h 14m 39s ⏱️
113 tests 106 ✅  7 💤 0 ❌
452 runs  424 ✅ 28 💤 0 ❌

Results for commit 6ff6e56.

[github-actions]

Published Unit Test Results

2 280 tests   2 280 ✅  2m 59s ⏱️
  128 suites      0 💤
    1 files        0 ❌

Results for commit 6ff6e56.