feat(dnsendpoint): Add Initial support for DNSEndpoint

[larivierec]

This adds initial support for DNSEndpoint CRD.
It looks similar to what has already been done for other CRDs except, this uses external-dns/v1alpha1 CRD.

I tried to use the crdSource coming from externaldns directly, however, it does not expose any means except a generic AddEventHandler and therefore, opted to use the same way as it's already done for other sources.

External-DNS source ref

Currently, dnsendpoint also only supports A record types.

If you have any ideas and ideas to do static tests i'm all ears, this is not a final PR.

Closes #239

e2e tests:

[DEBUG] plugin/k8s_gateway: Adding index test.garb.dev for DNSEndpoint test
[DEBUG] plugin/k8s_gateway: Adding index test2.garb.dev for DNSEndpoint test
[DEBUG] plugin/k8s_gateway: Adding index ingress.garb.dev for DNSEndpoint cloudflared

(⎈|k3s:home)➜  k8s_gateway git:(feature/support-dnsendpoint) ✗ dig test.garb.dev @127.0.0.1

; <<>> DiG 9.10.6 <<>> test.garb.dev @127.0.0.1
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 24465
;; flags: qr aa rd; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1
;; WARNING: recursion requested but not available

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;test.garb.dev.			IN	A

;; ANSWER SECTION:
test.garb.dev.		60	IN	A	192.168.30.1

;; Query time: 1 msec
;; SERVER: 127.0.0.1#53(127.0.0.1)
;; WHEN: Fri Oct 04 14:45:09 EDT 2024
;; MSG SIZE  rcvd: 71

[larivierec]

@networkop appreciate your review :)