Test cookie expiry with an injected clock

[hyperxpro]

Motivation:

CookieStoreTest stores cookies with Max-Age=1, sleeps 2000 ms and expects them evicted. ThreadSafeCookieStore expires a cookie when (now - createdAt) / 1000 > maxAge, so exactly 2000 ms must elapse on System.currentTimeMillis(). That clock ticks coarsely on Windows, the elapsed time read as just under 2000 ms, and the test failed on windows-latest JDK 11 with expected: <2> but was: <3>.

Modification:

Give ThreadSafeCookieStore a package-private constructor taking a LongSupplier clock; the public no-arg constructor is unchanged. Move the expiry check into ThreadSafeCookieStoreExpiryTest, which advances a fake clock instead of sleeping.

Result:

Cookie expiry is tested without Thread.sleep or the wall clock. No public API change.