feat: add transactionRetryIntervalFallback to the global config

[tabaktoni]

Motivation and Resolution

Enable a simple configuration for the users to speed up development tests, and also globally configure the retry interval for production.

Usage related changes

Set a globally retry interval for all channels.

// devnet
config.set('channelDefaults.options.transactionRetryIntervalFallback', 0);

// testnet - experiment with your RPC node to get the most performant value, default is conservative 5000ms
config.set('channelDefaults.options.transactionRetryIntervalFallback', 3000);

Development related changes

Set config in test fixture instead of prop override

Checklist:

• Performed a self-review of the code
• Rebased to the last commit of the target branch (or merged it into my branch)
• Linked the issues which this PR resolves
• Documented the changes in code (API docs will be generated automatically)
• Updated the tests
• All tests are passing

[PhilippeR26]

Sounds good.