refactor validation of generic_resolver rules to startup

[dtrai2]

• Move validation logic to __attrs_post_init__ in GenericResolverRule.
• Remove redundant error handling in GenericResolver processor.
• Update corresponding tests to reflect changes.

[djkhl]

looks good and works as expected :)

[ppcad]

Getters need to be updated on the fly in the generic resolver. They are going to be refreshed periodically to get updated data from the HTTP getter.
Therefore, raising a configuration error leads to problems, since this can happen when Logprep is already running.
I'm going to create a pull request for this.

[dtrai2]

Getters need to be updated on the fly in the generic resolver. They are going to be refreshed periodically to get updated data from the HTTP getter.
Therefore, raising a configuration error leads to problems, since this can happen when Logprep is already running.
I'm going to create a pull request for this.

but isn't it already working with the general config refresh we have in Logprep? That way the configuration is also reloaded periodically and in case an exception is thrown, Logprep will continue running with the previous configuration.