Deserialize custom resources with EnableStrict

[stoyanr]

How to categorize this PR?

/area control-plane
/kind enhancement
/priority 3
/platform openstack

What this PR does / why we need it:

• Adds the EnableStrict option to all places where a codec factory is created, to ensure that extension resource configs are always deserialized in "strict" mode. This means that resources with fields that are not allowed by the API schema will be rejected by validation and will cause errors (categorized as ERR_CONFIGURATION_PROBLEM) during reconciliation as well.
• Vendors g/g 1.20.0 (includes Deserialize custom resources with EnableStrict gardener#3804) to ensure that a strict decoder is used also for ControlPlaneConfig and WorkerConfig, and errors are correctly categorized.

Which issue(s) this PR fixes:
Fixes gardener/gardener-extension-provider-azure#270, see also gardener/gardener-extension-provider-azure#271 and gardener/gardener-extension-provider-gcp#249.

Special notes for your reviewer:

Release note:

Extension resource configs (`InfrastructureConfig`, `ControlPlaneConfigs`, `WorkerConfig`) are now deserialized in "strict" mode, including during validation by the admission webhook. This means that resources with fields that are not allowed by the API schema will be rejected by validation. Creating new shoots containing such resources will not be possible, and reconciling existing shoots will fail with an appropriate error until you manually update the shoot to make sure any extension resource configs contained in it are valid.

[rfranzke]

@dkistner @kon-angelo should we hold this PR? Are you validating a release?

[kon-angelo]

/hold

@rfranzke Yes we are validating a release. We can merge this in the coming days

[ialidzhikov]

The TestDefinitions need an update as well.

diff --git a/.test-defs/infrastructure-test.yaml b/.test-defs/infrastructure-test.yaml
index 341b20dd..dd7f648c 100644
--- a/.test-defs/infrastructure-test.yaml
+++ b/.test-defs/infrastructure-test.yaml
@@ -19,4 +19,4 @@ spec:
     --region="$REGION"
     --tenant-name="$TENANT_NAME"
     --user-name="$USER_NAME"
-  image: eu.gcr.io/gardener-project/3rd/golang:1.15.7
+  image: eu.gcr.io/gardener-project/3rd/golang:1.16.3
diff --git a/.test-defs/provider-openstack.yaml b/.test-defs/provider-openstack.yaml
index d742f7bc..31820e6e 100644
--- a/.test-defs/provider-openstack.yaml
+++ b/.test-defs/provider-openstack.yaml
@@ -16,4 +16,4 @@ spec:
     --loadbalancer-provider=$LOADBALANCER_PROVIDER
     --network-worker-cidr=$NETWORK_WORKER_CIDR

-  image: eu.gcr.io/gardener-project/3rd/golang:1.15.7
+  image: eu.gcr.io/gardener-project/3rd/golang:1.16.3

[stoyanr]

The TestDefinitions need an update as well.

Done

[rfranzke]

Can you please revendor the v1.20.0 tag now that it's released?

[stoyanr]

Can you please revendor the v1.20.0 tag now that it's released?

Done

[ialidzhikov]

/lgtm

[rfranzke]

Thanks @stoyanr, can you check why the verify step is failing?