[AIRFLOW-7108] Fix CloudSecretsManagerBackend invalid connections_prefix

[xinbinhuang]

GCP Secrets Manager only accepts [a-zA-Z0-9-_]* as its valid secret id key. This PR fixes the implementation and adds checks in the constructor.

Screenshot at GCP Console

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Issue link: AIRFLOW-7108

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[xinbinhuang]

Need to rebase after #7861 is merged

[zhongjiajie]

Should we add [WIP] in PR title avoid incorrect merge?

[codecov-io]

Codecov Report

Merging #7861 into master will increase coverage by 21.15%.
The diff coverage is 100.00%.

@@             Coverage Diff             @@
##           master    #7861       +/-   ##
===========================================
+ Coverage   65.44%   86.60%   +21.15%     
===========================================
  Files         927      927               
  Lines       44963    44972        +9     
===========================================
+ Hits        29425    38946     +9521     
+ Misses      15538     6026     -9512     

Impacted Files	Coverage Δ
.../providers/google/cloud/secrets/secrets_manager.py	100.00% <100.00%> (ø)
airflow/secrets/base_secrets.py	94.11% <100.00%> (ø)
airflow/kubernetes/volume_mount.py	44.44% <0.00%> (-55.56%)	⬇️
airflow/kubernetes/volume.py	52.94% <0.00%> (-47.06%)	⬇️
airflow/kubernetes/pod_launcher.py	47.18% <0.00%> (-39.44%)	⬇️
...viders/cncf/kubernetes/operators/kubernetes_pod.py	69.69% <0.00%> (-25.26%)	⬇️
airflow/kubernetes/refresh_config.py	50.98% <0.00%> (-23.53%)	⬇️
airflow/providers/google/cloud/operators/vision.py	99.63% <0.00%> (+0.36%)	⬆️
...osoft/azure/operators/azure_container_instances.py	78.28% <0.00%> (+0.65%)	⬆️
airflow/cli/cli_parser.py	98.13% <0.00%> (+0.93%)	⬆️
... and 492 more

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[kaxil]

Can you rebase your PR on master please

[xinbinhuang]

@zhongjiajie @kaxil Just rebased. Going through Travis now. Should be good to go after that

[xinbinhuang]

@zhongjiajie @kaxil Just rebased. Going through Travis now. Should be good to go after that

Travis green!. Let me know if you have any other comments.

[kaxil]

Thanks @xinbinhuang