[12.x] Expand Redis DurationLimiter tests

[miladev95]

Adds focused tests in tests/Redis/DurationLimiterTest.php for acquire(), tooManyAttempts(), clear(), block(), and window reset after decay.

[taylorotwell]

Do we have to actually use sleep? Can we fake the time travel?

[miladev95]

Do we have to actually use sleep? Can we fake the time travel?

I investigated using Carbon time travel, but DurationLimiter uses PHP's native
time() function in its Redis Lua scripts, which Carbon::setTestNow() can't mock.

Tested both approaches:

• With Carbon time travel: 2 tests fail
• With sleep(): All tests pass

ConcurrentLimiterTest also uses usleep() for the same reason. The sleep()
approach accurately tests real Redis TTL behavior.