feat(kuma-cp): multitenancy adjustments

[jakubdyszkiewicz]

Checklist prior to review

This PR introduces a couple of multitenancy improvements:

• Simplify interfaces
  • Removed HashingFunc. This is IMHO confusing. It's better to say that some things are tenant aware even if there is a single tenant in Kuma
  • Renamed Tenant to Tenants as it's imho confusing to have Tenant interface with method GetAllId() . Renamed TenantFn() to Tenants() in Runtime obj.
  • Introduce GetID() to Tenants so other implementations can fail if a tenant is missing.
• Add option to skip creating default tenant aware resources if tenants are managed in other way
• Introduce overridable global tenant and use it explicitly in components that are not tenant aware. Using it explicitly makes it easier to require tenant in other places.

• Link 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 a image registry) and it will work on Windows, system specific functions like syscall.Mkfifo have equivalent implementation on the other OS --
• Tests (Unit test, E2E tests, manual test on universal and k8s) --
• Do you need to update UPGRADE.md? --
• Does it need to be backported according to the backporting policy? --
• Do you need to explicitly set a > Changelog: entry here or add a ci/ label to run fewer/more tests?

[lukidzi]

Looks good and simpler!