pubsub/azuresb: new auth method to support Service principal/kubelet identity/Workload identity auth methods

[tsolodov]

new auth method to support Service principal/kubelet identity/Workload identity auth methods.(handled by Azure golang SDK)

How to use:
depends on method(Workload, kubelet, Service), set ENV variables:
AZURE_SERVICEBUS_HOSTNAME - to trigger new method

For service principal auth, set ENV variables described here

If you use workload/kubelet identities, ENV variables are injected by AKS, some details can be found here

closes #3359

was able to run performance test using new auth model:

AZURE_CLIENT_SECRET='secret' AZURE_CLIENT_ID=2f370f8b-XXXX-4c60-b3c7-XXXXX AZURE_TENANT_ID=XXXX-a475-466f-ab08-XXXX AZURE_SERVICEBUS_HOSTNAME=xxxxxx.servicebus.windows.net /opt/homebrew/bin/go test -benchmem -run=^$ -bench ^BenchmarkAzureServiceBusPubSub$ gocloud.dev/pubsub/azuresb

benchmark-topic
goos: darwin
goarch: arm64
pkg: gocloud.dev/pubsub/azuresb
BenchmarkAzureServiceBusPubSub/BenchmarkReceive-10         	       1	154489245124 ns/op	  64.73 MB/s	88464128 B/op	 1556345 allocs/op
--- BENCH: BenchmarkAzureServiceBusPubSub/BenchmarkReceive-10
    drivertest.go:1039: published 10000 messages
    drivertest.go:1049: MB/s is actually number of messages received per second


BenchmarkAzureServiceBusPubSub/BenchmarkSend-10            	       1	4310127584 ns/op	2320.12 MB/s	45803056 B/op	  805866 allocs/op
--- BENCH: BenchmarkAzureServiceBusPubSub/BenchmarkSend-10
    drivertest.go:1039: published 10000 messages
    drivertest.go:1049: MB/s is actually number of messages received per second
PASS
ok  	gocloud.dev/pubsub/azuresb	289.383s

Not sure how to test it(should be tested against Azure cloud with real credentials)

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[tsolodov]

PTAL

[tsolodov]

Hi @vangent , could you please take a look?

[codecov]

Codecov Report

Attention: 20 lines in your changes are missing coverage. Please review.

Comparison is base (8c8f558) 77.43% compared to head (aff0776) 77.37%.
Report is 2 commits behind head on master.

Files	Patch %	Lines
pubsub/azuresb/azuresb.go	20.00%	17 Missing and 3 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3360      +/-   ##
==========================================
- Coverage   77.43%   77.37%   -0.07%     
==========================================
  Files         104      104              
  Lines       13935    13951      +16     
==========================================
+ Hits        10790    10794       +4     
- Misses       2384     2396      +12     
  Partials      761      761              

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