dnsapi/dns_opnsense.sh: Refresh for OPNsense v25.7 series

[benyamin-codez]

Updates the dns_opnsense.sh Bourne shell script for OPNSense v25.7 series:

1. Fixes historical error in rm_record() [used incorrect response variable]
2. Improves debug messaging in rm_record()
3. Fixes _get_root() for change in OPNsense API
   • Response is now split into pseudo-rows
   • We now iterate through pseudo-rows for matching domainname field
4. Fixes _existingchallenge() for change in OPNsense API
   • Fixes unreliable regex for uuid
   • Adds domain regex and %domain field
5. Fixes historical error in _existingchallenge() [incorrect variable syntax]

Resolves #6467

[github-actions]

Welcome
READ ME !!!!!
Read me !!!!!!
First thing: don't send PR to the master branch, please send to the dev branch instead.
Please read the DNS API Dev Guide.
You MUST pass the DNS-API-Test.
Then reply on this message, otherwise, your code will not be reviewed or merged.
Please also make sure to add/update the usage here: https://github.com/acmesh-official/acme.sh/wiki/dnsapi2
注意: 必须通过了 DNS-API-Test 才会被 review. 无论是修改, 还是新加的 dns api, 都必须确保通过这个测试.

[benyamin-codez]

Welcome READ ME !!!!! Read me !!!!!! First thing: don't send PR to the master branch, please send to the dev branch instead. Please read the DNS API Dev Guide. You MUST pass the DNS-API-Test. Then reply on this message, otherwise, your code will not be reviewed or merged. Please also make sure to add/update the usage here: https://github.com/acmesh-official/acme.sh/wiki/dnsapi2 注意: 必须通过了 DNS-API-Test 才会被 review. 无论是修改, 还是新加的 dns api, 都必须确保通过这个测试.

No usage to update (it remains unchanged).
DNS-API-Test not applicable as the script executes against local BIND (named) instance.
Tested extensively at debug 3.

[benyamin-codez]

Suggest this PR in place of PR #6468.
@koelle25 : Kevin, what do you think?