Fix issue building urls with IPv6 IPs for ACME http-01 challenges

[stevendpclark]

Description

• We weren't properly encapsulating the IPv6 IP within the URL provided to the http client with [].
• Validate using netip.ParseAddr if we are a proper IPv6 address.
  • We aren't using net.IP.ToIPv4 as that will return true for IPv4 addresses encoded within an IPv6 ::ffff: prefix
• Even though the ACME new order handler will prohibit zone'd IPv6 addresses, we fix the URL encoding of the IPv6 address being sent into the http client to surround the escaped value in [] and encode the % with %25 in case we ever change that logic.

# ./acme.sh --issue --standalone --server http://127.0.0.1:8200/v1/pki/acme/directory --listen-v6 --domain 2600:1f11:482:a409:7dd4:59ab:ea06:b516
[Wed Oct 16 14:35:47 UTC 2024] Using CA: http://127.0.0.1:8200/v1/pki/acme/directory
[Wed Oct 16 14:35:47 UTC 2024] Standalone mode.
[Wed Oct 16 14:35:47 UTC 2024] Single domain='2600:1f11:482:a409:7dd4:59ab:ea06:b516'
[Wed Oct 16 14:35:48 UTC 2024] Getting webroot for domain='2600:1f11:482:a409:7dd4:59ab:ea06:b516'
[Wed Oct 16 14:35:48 UTC 2024] Verifying: 2600:1f11:482:a409:7dd4:59ab:ea06:b516
[Wed Oct 16 14:35:48 UTC 2024] Standalone mode server
[Wed Oct 16 14:35:49 UTC 2024] Processing. The CA is processing your order, please wait. (1/30)
[Wed Oct 16 14:35:53 UTC 2024] Success
[Wed Oct 16 14:35:53 UTC 2024] Verification finished, beginning signing.
[Wed Oct 16 14:35:53 UTC 2024] Let's finalize the order.
[Wed Oct 16 14:35:53 UTC 2024] Le_OrderFinalize='http://127.0.0.1:8200/v1/pki/acme/order/0434cc5a-12ab-e387-b778-e70f0565f0b0/finalize'
[Wed Oct 16 14:35:53 UTC 2024] Downloading cert.
[Wed Oct 16 14:35:53 UTC 2024] Le_LinkCert='http://127.0.0.1:8200/v1/pki/acme/order/0434cc5a-12ab-e387-b778-e70f0565f0b0/cert'
[Wed Oct 16 14:35:53 UTC 2024] Cert success.
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----
[Wed Oct 16 14:35:53 UTC 2024] Your cert is in: /root/.acme.sh/2600:1f11:482:a409:7dd4:59ab:ea06:b516_ecc/2600:1f11:482:a409:7dd4:59ab:ea06:b516.cer
[Wed Oct 16 14:35:53 UTC 2024] Your cert key is in: /root/.acme.sh/2600:1f11:482:a409:7dd4:59ab:ea06:b516_ecc/2600:1f11:482:a409:7dd4:59ab:ea06:b516.key
[Wed Oct 16 14:35:53 UTC 2024] The intermediate CA cert is in: /root/.acme.sh/2600:1f11:482:a409:7dd4:59ab:ea06:b516_ecc/ca.cer
[Wed Oct 16 14:35:53 UTC 2024] And the full-chain cert is in: /root/.acme.sh/2600:1f11:482:a409:7dd4:59ab:ea06:b516_ecc/fullchain.cer

TODO only if you're a HashiCorp employee

• Backport Labels: If this PR is in the ENT repo and needs to be backported, backport
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  • If this fixes a critical security vulnerability or severity 1 bug, it will also need to be backported to the current LTS versions of Vault. To ensure this, use all available enterprise labels.
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[github-actions]

Build Results:
All builds succeeded! ✅

[github-actions]

CI Results:
All Go tests succeeded! ✅

[victorr]

Looks good to me 👍

[kitography]

Looks great, very clean - well done