blob/azureblob: Use azidentity.NewDefaultAzureCredential as the default/fallback

[vangent]

No description provided.

[codecov]

Codecov Report

Merging #3161 (ebe52c2) into master (bb5165b) will increase coverage by 0.02%.
The diff coverage is 14.28%.

@@            Coverage Diff             @@
##           master    #3161      +/-   ##
==========================================
+ Coverage   72.79%   72.81%   +0.02%     
==========================================
  Files         113      113              
  Lines       14385    14385              
==========================================
+ Hits        10472    10475       +3     
+ Misses       3187     3185       -2     
+ Partials      726      725       -1     

Impacted Files	Coverage Δ
blob/azureblob/azureblob.go	84.06% <14.28%> (ø)
pubsub/rabbitpubsub/rabbit.go	80.56% <0.00%> (-0.63%)	⬇️
blob/s3blob/s3blob.go	89.71% <0.00%> (+0.27%)	⬆️
runtimevar/awssecretsmanager/awssecretsmanager.go	83.49% <0.00%> (+1.45%)	⬆️

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