[PIP-60] [Proxy-Client] Support SNI routing for Pulsar CPP client

[rdhabalia]

Motivation

#8957 was added incorrectly and it was not supporting SNI routing for CPP client library.
This PR adds support of SNI roting to Pulsar CPP client library and allows users to connect with Pulsar broker using SNI Proxy.
User can configure Pulsar client lib to use SNI routing and proxy by adding below configuration

const std::string lookupUrl = "pulsar+ssl://broker-url:6651";
const std::string proxyUrl = "pulsar+ssl://sni-proxy-url:6651";
const std::string topicName = "persistent://pulsar/stg-use1/ns1/t1";
const std::string certFile = "/client-cert.pem";
const std::string keyFile = "/client-key.pem";
const std::string trustFile = "/trust-store.pem";

ClientConfiguration conf;
conf.setUseTls(true);
conf.setTlsAllowInsecureConnection(false);
conf.setTlsTrustCertsFilePath(trustFile);
conf.setAuth(AuthTls::create(std::move(certFile), std::move(keyFile)));
conf.setProxyServiceUrl(proxyUrl);
conf.setProxyProtocol(ClientConfiguration::SNI);

Client client(lookupUrl, conf);

Modifications

Added a support of SNI routing by adding new APIs to configure proxy URL and protocol.

ClientConfiguration::setProxyServiceUrl(..)
ClientConfiguration::setProxyProtocol(..)

Verifying this change

• Make sure that the change passes the CI checks.

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This change is a trivial rework / code cleanup without any test coverage.

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This change is already covered by existing tests, such as (please describe tests).

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This change added tests and can be verified as follows:

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• Added integration tests for end-to-end deployment with large payloads (10MB)
• Extended integration test for recovery after broker failure

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[BewareMyPower]

Overall LGTM except the const use in the method signatures.