NIFI-16078 - Fix StandardHashiCorpVaultClientService for non-token authentication

[pvillard31]

Summary

NIFI-16078 - Fix StandardHashiCorpVaultClientService for non-token authentication

In NiFi 2.10.0, spring-vault-core was upgraded 4.0.1 → 4.1.0. Non-token auth methods now build their client via AbstractVaultConfiguration.vaultClient(), which looks up a clientHttpRequestFactoryWrapper bean; AWS EC2 / Azure MSI also go through restClient() → getRestTemplateFactory(). Alsok, NiFi's getRestTemplateFactory() override was removed.

NiFi configures HashiCorpVaultConfiguration programmatically with an empty StaticApplicationContext, so these bean lookups fail. Token authentication is unaffected (it needs no Vault client).

With this change, HashiCorpVaultConfiguration.setClientHttpRequestFactory(...) registers the request factory as the clientHttpRequestFactoryWrapper bean. We also restore the getRestTemplateFactory() override built from that same factory. And StandardHashiCorpVaultCommunicationService passes its configured (SSL Context Service–aware) factory before clientAuthentication(), so the auth client uses the same TLS material.

Added new unit tests cover Kubernetes and AWS EC2 authentication; both reproduce the reported failure without the fix.

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