[1.1] Helm 3 release existence check

werf-converge and werf-deploy commands will refuse to work when helm 3 release with the same name as target helm 2 release exists in the current namespace.

This check protects existing helm 3 release when your project has already been migrated from helm 2 to helm 3, but for some reason werf v1.1 tries to redeploy this release.