refactor(rules): organize code in the packages, prepare for inbound rules

[lobkovilya]

Motivation

• with the introduction of inbound rules, a single file rules.go is insufficient
• new inbound rules are going to introduce a new entry type (i.e. to[i] has targetRef and default fields, while rules[i] is going to have default, matches, targetRef fields). It's easier to use generics, like

  type WithPolicyAttributes[T any] struct {
  	Entry T
  
  	TopLevel  common_api.TargetRef
  	Meta      core_model.ResourceMeta
  	RuleIndex int
  }

  to share the code between inbound and outbound rules (see packages merge, sort, common)

Supporting documentation

Check commit to see how new inbound rules are implemented

[lobkovilya]

there are just copies of functions from rules.go in this file, you can skip reviewing this

[github-actions]

Reviewer Checklist

🔍 Each of these sections need to be checked by the reviewer of the PR 🔍:
If something doesn't apply please check the box and add a justification if the reason is non obvious.

• Is the PR title satisfactory? Is this part of a larger feature and should be grouped using > Changelog?
• PR description is clear and complete. It Links to relevant issue as well as docs and UI issues
• This will not break child repos: it doesn't hardcode values (.e.g "kumahq" as an image registry)
• IPv6 is taken into account (.e.g: no string concatenation of host port)
• Tests (Unit test, E2E tests, manual test on universal and k8s)
  • Don't forget ci/ labels to run additional/fewer tests
• Does this contain a change that needs to be notified to users? In this case, UPGRADE.md should be updated.
• Does it need to be backported according to the backporting policy? (this GH action will add "backport" label based on these file globs, if you want to prevent it from adding the "backport" label use no-backport-autolabel label)

[lahabana]

Can we do proper git mv ? This would greatly simplify this PR

[lobkovilya]

I think it's already moved where possible, sometimes the code is copied from rules.go to more specific packages and in this case git mv won't help