Integration test setup for AKV

[berndverst]

In order to test the various authentication methods for KeyVault several credentials and component configurations need to be configured.

This PR makes the necessary changes.

[berndverst]

This PR can be verified like so:

bash setup-azure-conf-test.sh --user="XXXXX@microsoft.com" --location="WestUS2"
source $HOME/azure-conf-test/XXXXX-conf-test-config.rc

 go test -v -tags=conftests -count=1 ./tests/conformance -run="TestSecretStoreConformance/azure.keyvault.serviceprincipal"
 go test -v -tags=conftests -count=1 ./tests/conformance -run="TestSecretStoreConformance/azure.keyvault.certificate"

Note that you need to run in a particular environment with MSI enabled (and the identity having the correct permission) to run the remaining test:

 go test -v -tags=conftests -count=1 ./tests/conformance -run="TestSecretStoreConformance/azure.keyvault.managedidentity"

[berndverst]

@CodeMonkeyLeet you previously suggested creating different configs for the different authentication mechanisms. Thoughts on this PR?

I am planning to call the new authentication methods as conformance tests via the new integration test framework (I will need to spin up the managed identity enabled environment from there), though I could also enable serviceprincipal auth directly via the test matrix here.

[berndverst]

Removed the Managed Identity configuration from the conformance tests since it can't be run there. Will instead consider creating a sample / quickstart.

[CodeMonkeyLeet]

LGTM

[codecov]

Codecov Report

Merging #1206 (029ca1d) into master (b2752d0) will increase coverage by 0.00%.
The diff coverage is 0.00%.

@@           Coverage Diff           @@
##           master    #1206   +/-   ##
=======================================
  Coverage   35.07%   35.07%           
=======================================
  Files         147      147           
  Lines       12622    12624    +2     
=======================================
+ Hits         4427     4428    +1     
  Misses       7727     7727           
- Partials      468      469    +1     

Impacted Files	Coverage Δ
tests/conformance/common.go	16.86% <0.00%> (-0.14%)	⬇️
state/cloudstate/cloudstate_crdt.go	9.09% <0.00%> (+0.41%)	⬆️

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