Improve logging

[antoineco]

What this PR does / why we need it:

Improves the overall clarity of existing log messages.

Includes some minor refactoring of the store's Get...() methods to use the same func (key string) ... signature consistently.

Which issue this PR fixes:

fixes #2712
follow-up on #2639

[antoineco]

/assign @aledbf
/assign @ElvinEfendi

[codecov-io]

Codecov Report

Merging #2732 into master will decrease coverage by 0.05%.
The diff coverage is 22.68%.

@@            Coverage Diff             @@
##           master    #2732      +/-   ##
==========================================
- Coverage   40.96%   40.91%   -0.06%     
==========================================
  Files          72       73       +1     
  Lines        5085     5101      +16     
==========================================
+ Hits         2083     2087       +4     
- Misses       2713     2725      +12     
  Partials      289      289

Impacted Files	Coverage Δ
internal/ingress/controller/store/configmap.go	0% <0%> (ø)	⬆️
...nal/ingress/controller/store/ingress_annotation.go	0% <0%> (ø)
internal/ingress/controller/store/endpoint.go	0% <0%> (ø)	⬆️
internal/ingress/controller/endpoints.go	94.33% <100%> (+0.1%)	⬆️
internal/ingress/controller/store/ingress.go	71.42% <100%> (ø)	⬆️
internal/ingress/controller/store/secret.go	71.42% <100%> (ø)	⬆️
internal/ingress/controller/store/service.go	57.14% <100%> (ø)	⬆️
internal/ingress/controller/store/backend_ssl.go	44.21% <27.27%> (+0.59%)	⬆️
internal/ingress/controller/store/store.go	60.18% <33.33%> (+1.32%)	⬆️
internal/ingress/controller/controller.go	2.35% <6.25%> (-0.05%)	⬇️
... and 1 more

---

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[aledbf]

@antoineco I like the NotExistsError approach

[aledbf]

/lgtm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: aledbf, antoineco

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