SSL CA support for the Java SDK

[salaboy]

Expected Behavior

Similar to temporal we should be able to set the CA key and path:

 String clientKeyPath = getenv("TEMPORAL_MTLS_PRIVATE_KEY_PATH");
        String clientCertPath = getenv("TEMPORAL_MTLS_CERT_PATH");

        try {
            // Generate an SSL context
            InputStream clientCertInputStream = new FileInputStream(clientCertPath);
            InputStream clientKeyInputStream = new FileInputStream(clientKeyPath);
            SslContext sslContext = SimpleSslContextBuilder.forPKCS8(clientCertInputStream, clientKeyInputStream).build();

            // Set the Service Stub options (SSL context and gRPC endpoint)
            WorkflowServiceStubsOptions stubsOptions = WorkflowServiceStubsOptions
                .newBuilder()
                .setSslContext(sslContext)
                .setTarget(gRPCEndpoint)
                .build();

Example: https://github.com/temporalio/documentation/blob/main/sample-apps/java/client/cloudserver-client-sample/src/main/java/clientsample/YourCallerApp.java

Actual Behavior

If the app is behind a proxy with their own trust store the SDK needs to support setting the SSL context.

Steps to Reproduce the Problem

Release Note

RELEASE NOTE:

[salaboy]

This seems very relevant: https://stackoverflow.com/questions/48353718/why-does-managedchannelbuilder-not-have-tls-parameters-for-making-tls-connection

[cicoyle]

#1361