Brush up the eviction handler implementation

[tatsuya6502]

As of now (commit #f7a15e24), the following issues might be present with the eviction handler:

1. invalidate an existing entry will always trigger the eviction handler with RemovalCause::Explicit.
   • a. But there are chances that entry has been already expired. In such case, the eviction handler should be triggered with RemovalCause::Expired.
   • b. The same thing applies to invalidate_all.
2. There is no code path for RemovalCause::Replaced.
   • a. We should also select RemovalCause::Replaced or RemovalCause::Expired based on the expiration status of the entry.

For 1-a and 2-a, see moka's this unit test: moka sync/cache.rs#L4270-L4280

[tatsuya6502]

Also an internal do_upsert_with_hash method should check whether the existing entry is expired or not. If expired, it should skip to call the update closure.

mini-moka/src/sync/base_cache.rs

Lines 295 to 296 in f7a15e2

	let mut old_value = entry.value.clone();
	update(&mut old_value, &mut value);

[tatsuya6502]

Since this feature is not released yet, I am setting enhancement label rather than bug.