fix: negative tests

[Alex-GF]

These are some points that need to be known when reviewing the PR:

• All comments within the negative tests have been removed and now run the desired tests.
• I have corrected the suite of real world pricing that were used to perform positive validation of the parsing process. Now, the dataset of real world pricing is up-to-date with the one used in Pricing4TS. In addition, I have parametrized their test suite, which had more than 120 hand-coded tests with similar assertions.
• According to Pricing2Yaml, if the availableFor field is not present within an add-on, it will be available for al plans. That's why, instead of throwing an exception, I have implemented such behavior.
• I have also modified a behavior related to version management. If the version field is not present within a Pricing2Yaml specification, it will throw an error.

Please, take this comments into consideration when modifying the documentation this week ;)