feat: Aggregate linting errors and added functionality to pass a glob argument

[nielstenboom]

What this PR does / why we need it: This PR implements two things:

• The linting errors will now be aggregated in a list and returned at the end, this means that all the errors encountered while linting will show to the user. Instead of encountering an error, exiting immediately and then the user has to run lint multiple times. Also the current error implementation did not allow for linting of multiple values.yaml files. If an error was encountered in the first file, the rest of the values would be skipped.
• The ability to pass a glob pattern to look for values.yaml files, currently this was hardcoded to ci/*values.yaml.

Which issue this PR fixes fixes https://github.com/helm/chart-testing/issues/171

Special notes for your reviewer: Not 100% sure if the Errors list I added has any implications for the ct test command. Please let me know if this is the case. Thanks!