Allow overriding PATCH vs PUT for updates of select resources

[thomas11]

Update: since there are resources where PATCH is also the Create method, this PR doesn't work as is. We cannot express three options with one boolean UpdateMethod:

1. both PUT
2. PUT for create, PATCH for update
3. both PATCH

---

Currently, every resource where the spec defines a PUT operation is created and updated via PUT. This is incorrect for a small number of resources which should be created via PUT but updated via PATCH. Postgres Server, e.g., will be recreated when updated via PUT when certain properties are changed.

This PR decouples determining the create and the update operation for a resource. It splits CreateOrUpdate of the Azure client into Create and Update. An addition to the Postgres integration test shows that the password of a server can now be updated without replacement.

Resolves #3961

[github-actions]

Does the PR have any schema changes?

Looking good! No breaking changes found.
No new resources/functions.

[codecov]

Codecov Report

Attention: Patch coverage is 73.33333% with 8 lines in your changes missing coverage. Please review.

Project coverage is 57.51%. Comparing base (c85f387) to head (b9c21a7).

Files with missing lines	Patch %	Lines
provider/pkg/gen/schema.go	73.68%	3 Missing and 2 partials ⚠️
provider/pkg/provider/provider.go	50.00%	1 Missing ⚠️
...ovider/pkg/resources/customresources/custom_pim.go	66.66%	1 Missing ⚠️
...esources/customresources/custom_postgres_config.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3983      +/-   ##
==========================================
+ Coverage   57.49%   57.51%   +0.02%     
==========================================
  Files          82       82              
  Lines       13078    13092      +14     
==========================================
+ Hits         7519     7530      +11     
- Misses       4984     4986       +2     
- Partials      575      576       +1     

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