refactor(xds): route builder

[mmorel-35]

This moves the RouteBuilder in the github.com/kumahq/kuma/pkg/xds/envoy/routes package.
Only the reusable Configurers and builders are moved in this package to be reused everywhere the building of a route is need.

This MR is only including the moving into a new package.
Once #7183 is merged and this one is too, I'll create a new MR to replace all envoy config v3 Route definitions with the use of RouteBuilder

Checklist prior to review

• Link to relevant issue as well as docs and UI issues -- xDS generators should require resource names #2538
• 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?

[slonka]

@lobkovilya or @jakubdyszkiewicz can you take a look at this one when you're online?

[slonka]

@jakubdyszkiewicz or @lobkovilya can you look at this PR when you have some time?

[jakubdyszkiewicz]

looks good. Sorry for the long feedback loop on this