Add support for WithEvents to ConcurrentLfuBuilder

[bitfaster]

• Builder now supports WithEvents. Previously, ConcurrentLfu did not have events, so this preserves existing behavior for the builder.
• Builder returns internal class FastConcurrentLfu which uses the NoEventsPolicy. It supports both access order and time based expiry via generic parameters. This means we can have a single class for both expiry modes. Since this is internal, user cannot see the ugly generics. We can later consider providing public FastConcurrentLfu and FastConcurrentTLfu and clean up the generics.
• Implemented a test class base with derived test classes to verify basic functionality for access order, expire after access, expire after write and expire after policies.

[bitfaster]

@copilot fix the failing tests. Do not make any changes except for fixing the tests.

[Copilot]

@copilot fix the failing tests. Do not make any changes except for fixing the tests.

Fixed in de473ca. The root cause was that FastConcurrentLfu (the new default without events) didn't implement ITimePolicy/IDiscreteTimePolicy, so Policy.ExpireAfterWrite/ExpireAfterAccess/ExpireAfter.HasValue returned false. Added CreatePolicy() to properly detect the expiry policy type via typeof(P) check and implemented the time policy interface. Also updated TestScheduler to use WithEvents() since the default now returns FastConcurrentLfu instead of ConcurrentLfu.

[coveralls]

coverage: 99.169%. first build — users/alexpeck/lfubuilderevents into main