CI: fix Helm linting and testing

[yorugac]

CI workflows for linting and testing Helm should be enabled for all PRs that include changes to chart's folder. Those workflows are set up in that way now; however, it appears that in case of third-party PR, the workflow fails:

It might be the branch is not being pulled correctly, given the renaming GA is doing automatically. Or there might be some error with how ct is being called.

[yorugac]

Hopefully fixed with the PRs:
#444
#447
#448
#449

Tested for external PRs here:
#445
#446