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 81.65548% with 82 lines in your changes missing coverage. Please review.
✅ Project coverage is 69.07%. Comparing base (19944e7) to head (48e2cf6).

Files with missing lines	Patch %	Lines
internal/lbspec/opts.go	62.80%	45 Missing ⚠️
internal/hcops/load_balancer.go	80.18%	13 Missing and 8 partials ⚠️
internal/testsupport/klog.go	0.00%	11 Missing ⚠️
hcloud/load_balancers.go	90.69%	3 Missing and 1 partial ⚠️
internal/hcops/mocks.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@                        Coverage Diff                         @@
##           split/core-a-typed-annotations    #1329      +/-   ##
==================================================================
- Coverage                           70.11%   69.07%   -1.05%     
==================================================================
  Files                                  29       32       +3     
  Lines                                2794     2658     -136     
==================================================================
- Hits                                 1959     1836     -123     
- Misses                                643      658      +15     
+ Partials                              192      164      -28     

Flag	Coverage Δ
e2e	46.30% <59.40%> (+1.20%)	⬆️
unit	64.67% <76.06%> (-1.83%)	⬇️

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