update EnvironmentCredential and azure.core.util.Configuration

[cxznmhdcxz]

Updated EnvironmentCredential to support env vars for UsernamePasswordCredential and ClientCertificateCredential. Added PROPERTY_AZURE_CLIENT_CERTIFICATE_PATH to azure.core.util.Configuration.

same code as #7337, as #7337 was reverted

[alzimmermsft]

This build is failing since Identity is relying on the released version of Azure Core and these changes depend on source code Azure Core, this is why the Identity from source validation job is passing but all others are failing. To fix this the dependency version of Azure Core will need to be changed to unreleased_com.azure:azure-core.

[g2vinay]

Rebase with master.
and update core dependency to this

<dependency>
  <groupId>com.azure</groupId>
  <artifactId>azure-core</artifactId>
  <version>1.4.0-beta.1</version> <!-- {x-version-update;unreleased_com.azure:azure-core;dependency} -->
</dependency>