add streamer refresh interval

[Graeme22]

Description

Previously, the "acceptAggregationPeriod" of DXLink channels was hardcoded to a value of 10, leading to unacceptably long delays between quotes in many scenarios. This fixes the problem by adding a new streamer parameter, refresh_interval, which allows each user to configure the value as desired. In addition, the default value is now 0.1, which is close to real-time, rather than the unwieldy 10, so most users will get immediate benefits without any changes.

Related issue(s)

Fixes #211

Pre-merge checklist

• Code formatted correctly (check with make lint)
• Code implemented for both sync and async
• Passing tests locally (check with make test, make sure you have TT_USERNAME, TT_PASSWORD, and TT_ACCOUNT environment variables set)
• New tests added (if applicable)

Please note that, in order to pass the tests, you'll need to set up your Tastytrade credentials as repository secrets on your local fork. Read more at CONTRIBUTING.md.