[0.8.0] Merge `run` interfaces

What's Changed

Breaking changes

• Option :timeout renamed to :checkout_timeout.

  • Reason: This option configures only the waiting time for worker from the pool, not the task's work time. This naming should be more understandable on the call site.

    # Before
    Poolex.run(:my_awesome_pool, fn worker -> some_work(worker) end, timeout: 10_000)
    
    # After
    Poolex.run(:my_awesome_pool, fn worker -> some_work(worker) end, checkout_timeout: 10_000)

• Poolex.run/3 returns tuple {:error, :checkout_timeout} instead of :all_workers_are_busy.

  • Reason: It is easier to understand the uniform format of the response from the function: {:ok, result} or {:error, reason}.

• Poolex.caller() type replaced with struct defined in Poolex.Caller.t().

  • Reason: We need to save unique caller references.

• Poolex.run!/3 was removed in favor of Poolex.run/3. The new unified function returns {:ok, result} or {:error, :checkout_timeout} and not handles runtime errors anymore.

  • Reason: We should not catch errors in the caller process. The caller process itself must choose how to handle exceptions and exit signals.

Fixed

• Fixed a bug when workers get stuck in busy status after checkout timeout.