Add product_chain and version_chain to AMQP client properties

[Rahmeen14]

Problem statement

Allow wrapper libraries to override product and version client properties, and add two new pipe-delimited fields (product_chain and version_chain) for full library stack traceability in the RabbitMQ management UI.
Previously, generateClientProperties() always overwrote product and version with rmqcpp's values, making it impossible for wrapper libraries to identify themselves.

Proposed changes

• Extract setChainProperties() helper from generateClientProperties()
• If the caller provides product_chain/version_chain, append rmqcpp to the chain
• If the caller only provides product/version (no chains), build the chain from both
• If nothing is provided, initialize the chain with rmqcpp's own identity
• All .thebsl::string() calls guarded with .isbsl::string() type checks

Remaining work

• Unit Tests
• Integration Tests
• Documentation