[QA] Snapshot testing

[prabhu]

We have many repotests that invoke cdxgen with a range of repos but don't validate the results :)

This issue is to seek community help to setup a snapshot testing workflow.

Requirements

• [ ] We use jest currently. Can we use jest snapshot testing as well?
• [x] How do we deal with attributes such as timestamps that can change, thus breaking such tests?
• [x] How do we deal with ordering (of files and components), which relies on the filesystem and the output from tools and can change based on the runner, version of the tools, weather, etc?
• [ ] How do we deal with snapshot updates where the changes are genuine improvements?

Bugs

Some of the bugs that escaped our current batch of repotests.

https://github.com/CycloneDX/cdxgen/issues/937