Allow users to have an option to save or send CCU

[ishantiw]

Description

Currently in ChainConnectorPlugin we simply create a CCU and send it using the privateKey set in the config.
We can give more flexibility to the user by saving the CCUs and exposing it via endpoints so that the user can send these CCUs when they want to send it (maybe at the time when fee is low to get in TxPool).

In order to achieve this,

• We can add a boolean property where user can specify whether to send transaction or save it
• When sending the transaction we can check this property and decide whether to send or save

Acceptance Criteria

• Should have all the relevant unit test cases