feat: refactor lookup logic

[agaffney]

This commit does the following:

• support lookup of more than NS from local storage
• add convenience function for converting from our storage format to dns.RR
• remove NS lookup logic for fallback servers and pass along query verbatim if not in local storage
• remove (now) unneeded state helper function

Fixes #107 and #159

[agaffney]

$ dig @localhost -p 8053 foo.county.cardano

; <<>> DiG 9.18.18-0ubuntu0.22.04.2-Ubuntu <<>> @localhost -p 8053 foo.county.cardano
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 34931
;; flags: qr rd; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 1
;; WARNING: recursion requested but not available

;; QUESTION SECTION:
;foo.county.cardano.		IN	A

;; AUTHORITY SECTION:
county.cardano.		999	IN	NS	ns1.county.cardano.

;; ADDITIONAL SECTION:
ns1.county.cardano.	999	IN	A	172.28.0.2

;; Query time: 0 msec
;; SERVER: 127.0.0.1#8053(localhost) (UDP)
;; WHEN: Wed May 29 16:50:29 CDT 2024
;; MSG SIZE  rcvd: 116

$ dig @localhost -p 8053 ns1.county.cardano

; <<>> DiG 9.18.18-0ubuntu0.22.04.2-Ubuntu <<>> @localhost -p 8053 ns1.county.cardano
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 64798
;; flags: qr rd; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0
;; WARNING: recursion requested but not available

;; QUESTION SECTION:
;ns1.county.cardano.		IN	A

;; ANSWER SECTION:
ns1.county.cardano.	3600	IN	A	172.28.0.2

;; Query time: 0 msec
;; SERVER: 127.0.0.1#8053(localhost) (UDP)
;; WHEN: Wed May 29 16:50:30 CDT 2024
;; MSG SIZE  rcvd: 70

$ dig @localhost -p 8053 www.google.com

; <<>> DiG 9.18.18-0ubuntu0.22.04.2-Ubuntu <<>> @localhost -p 8053 www.google.com
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 45967
;; flags: qr rd ra; QUERY: 1, ANSWER: 6, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 512
;; QUESTION SECTION:
;www.google.com.			IN	A

;; ANSWER SECTION:
www.google.com.		199	IN	A	142.250.114.147
www.google.com.		199	IN	A	142.250.114.104
www.google.com.		199	IN	A	142.250.114.99
www.google.com.		199	IN	A	142.250.114.106
www.google.com.		199	IN	A	142.250.114.103
www.google.com.		199	IN	A	142.250.114.105

;; Query time: 59 msec
;; SERVER: 127.0.0.1#8053(localhost) (UDP)
;; WHEN: Wed May 29 16:50:32 CDT 2024
;; MSG SIZE  rcvd: 223