chore: Refactor file resolving

[c-pius]

Description

Changes proposed in this pull request:

• addresses feat: Generate .spec.resources kyma-project/modulectl#73 (comment)
• we separate URL to tmp file resolving to a separate class that can be reused for both manifest and defaultCR
• reading of defaultCR data moved out of moduleconfig_reader (separation of concerns, and we already have a specialized FileReader service doing that)
• now we have a clean moduleconfig_reader (is only reading and validating the user provided module config, doesn't change the inputs)

Related issue(s)

[ruanxin]

Do we agree to only take remote link as input but not file anymore?

link must be a valid web URL (http* and not file://)

Then is this filepath code still in use?

[c-pius]

Right now it is. I would do a separate PR to deprecate it to make this change more explicit. Also we need to double check if we should do the same in other places (right now we used it at least for manifest and defaultCR).

[ruanxin]

I doubt we use it elsewhere, but I'm fine covering this in another PR or even an issue. tbh, I'm not so confident that I can remember this comment after it merged. 😄