Allow customer configuration of duplicate token filter in default provider

[rday]

Problem: The cuckoo filter used to detect duplicate tokens has a default capacity of (1 << 20) - 1. This is certainly too large for tracking tokens between key rotations. We should allow customers to configure their own filter size similar to how they configure the key_rotation_period.

Possible Solutions:

• Add a field to the Provider struct
• Provide some data on expected connections/sec and key_rotation_period to pick a reasonable value.

[camshaft]

Closing for now. We can reopen if requested.