[1.4.0] Worker shutdown delay support

What's Changed

Added

• New option worker_shutdown_delay for delayed shutdown of overflow workers. Allows to specify a delay (in ms) before terminating overflow workers after they are released. See the new guide for details.
• New option idle_overflowed_workers_impl for customizing the implementation of idle overflowed workers storage.
• Strong runtime pool init options validation.

Changed

Breaking changes

• Function get_debug_info/1 moved from Poolex to Poolex.Private.DebugInfo (according to the issue).
• Function Poolex.get_state/1 was removed.
• Minimum required version of Elixir bumped to ~> 1.17 and Erlang/OTP to ~> 25.

Full Changelog: v1.3.0...v1.4.0