Introduce fetchViaCommits configuration | Offers a new feature to solve an edge case resulting in old PRs not being included in changelog for squash merges

[mikepenz]

• honor authorDate and commitDate seperatly when detecting the PR date range to consider
• use the right commit for from date
• introduce new getForCommitHash to retrieve PRs based on hashes
• reorganize pull request filtering -> if we get PRs from commit hash, open PRs are already included, neither filtering is
• significantly simplify logic for results from commit hashes (only deduping needed) + filter if we don't want open PRs
• introduce new configuration fetchViaCommits which is best suited for environments with shorter diffs and/or squash merging (1 api request per commit)
• update tests for new configuration option