Client: Improve its creation flow and its options

[jeevatkm]

List of Resty client updates -

• Provide the ability to update timeout values
• Add Read-Write Mutex into the client struct to make all the client properties thread-safe. All the exported fields will become getter methods, e.g., client.BaseURL => client.BaseURL()
• Improve TLS config handling
• Improve Transport handling
• Make middleware composable
• Remove DualStack from net.Dialer since its deprecated
• Remove http.Client.Timeout in favor of Request Context cancellation with timeout
  • Refactor from client.SetTimeout to client.SetRequestTimeout
• Remove deprecated method client.SetHostURL