refactor: use a spec model for annotation extraction

[lukasmetzner]

Introduce internal/lbspec, which resolves a Service and the cluster-wide
configuration into a Spec describing the desired state, and which builds the
API opts from it.

• An invalid annotation now fails the whole reconcile instead of only the
  step that happened to read it. A typo in an HTTP annotation therefore also
  stops node targets from being updated.
• The remaining 5 hclbServiceOptsBuilder op label values disappear from
  hcloud_ccm_operations_total, and resolveCertificates is added.
• Certificates are resolved once per Service rather than once per port, and
  on the reconcile context instead of a detached 5s timeout.
• An empty name annotation no longer tries to rename the Load Balancer to the
  empty string, and an empty hostname annotation no longer publishes an empty
  hostname as the ingress address.
• private-ipv4 is parsed, so the private network address is compared as an
  address rather than as the literal annotation text.

[codecov]

Codecov Report

❌ Patch coverage is 82.51599% with 82 lines in your changes missing coverage. Please review.
✅ Project coverage is 69.17%. Comparing base (ec8fd02) to head (9cf4024).

Files with missing lines	Patch %	Lines
internal/lbspec/opts.go	62.80%	45 Missing ⚠️
internal/hcops/load_balancer.go	80.55%	13 Missing and 8 partials ⚠️
internal/testsupport/klog.go	0.00%	11 Missing ⚠️
hcloud/load_balancers.go	91.48%	3 Missing and 1 partial ⚠️
internal/hcops/mocks.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1329      +/-   ##
==========================================
- Coverage   70.11%   69.17%   -0.94%     
==========================================
  Files          29       32       +3     
  Lines        2794     2667     -127     
==========================================
- Hits         1959     1845     -114     
- Misses        643      658      +15     
+ Partials      192      164      -28     

Flag	Coverage Δ
e2e	46.17% <57.86%> (+1.07%)	⬆️
unit	64.79% <77.18%> (-1.71%)	⬇️

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[lukasmetzner]

Kubernetes events example for a Service object:

  Normal   EnsuringLoadBalancer           2s (x3 over 17s)   service-controller               Ensuring load balancer
  Warning  InvalidLoadBalancerAnnotation  2s (x3 over 17s)   hcloud-cloud-controller-manager  Invalid Load Balancer annotation "load-balancer.hetzner.cloud/use-private-ip": strconv.ParseBool: parsing "123": invalid syntax
  Warning  InvalidLoadBalancerAnnotation  2s (x3 over 17s)   hcloud-cloud-controller-manager  Invalid Load Balancer annotation "load-balancer.hetzner.cloud/protocol": invalid protocol: httpl
  Warning  SyncLoadBalancerFailed         2s (x3 over 17s)   service-controller               Error syncing load balancer: failed to ensure load balancer: hcloud/loadBalancers.EnsureLoadBalancer: 2 Load Balancer annotation(s) are invalid