test: mock maven and npm providers in unitests

[zvigrinberg]

Description

For maven-Java and npm-javascript package managers/providers, mock/stub interactions with mvn and npm cli tools.
that is, instead of actually invoking the cli, prepare files for each use case that will read the output of that file and will put it in the temp output file that the regular logic flow works with.

Motivations and Reasons

1. In pure unit-test , only the logic of the API library should be checked, and not the integration with package managers.
   Integration with package managers( and with exhort backend) will be tested in integrations tests.

2. critical reason to mock/stub interactions with package manager - in npm, from time to time, the versions are changed, if the package-lock.json is changed, and in this case, for component analysis, it might break the tests and force you to change the expected sbom.json files from time to time.

3. It takes a lot of time to run tests ( especially in case of maven).

Checklist

• I have followed this repository's contributing guidelines.
• I will adhere to the project's code of conduct.

Additional information

Anything else?