added `Thread` class, corrections, additional tests and libuv examples

• threading feature requires PHP ZTS, and not fully working.
• thread tests working most part, some works on Windows, segmentation on Linux, they are skipped for now.
• uv_queue_work is used to the mimic missing uv_thread_* features from libuv extension ext-uv .
• added additional libuv only examples showing actual execution flow among each other handles.
• added staging Channels class for threads, but not working the same way as Spawn/Parallel, needs a lot of work, mostly likely not even possible.
• various other corrections.

4.0.2

Update Parallel.php

Embed `opis/closure` to address/fix PHP 8.1 compatibility without FFI

• Embedded: opis/closure to directly address all issues in opis/closure#102.
  • Found removal of "implements Serializable" from class causes errors for PHP 7.3 and less, so restored, but changed logic for PHP 7.4+
• Added: reset() to Globals class, test, update doc-blocks.
• Moved: libuv UV stubs into own folder, fix/update code coverage to ignore.

General reworking to include `spatie/async` behavior without restrictions, issues.

• Updated "how to integrate" section, and documented differences with original author's spatie/async package.
  • Some of these changes was part of previous fork PR spatie/async#56, others fix or address many issues raised in: spatie/async#168, spatie/async#147, spatie/async#162, spatie/async#164, spatie/async#168, spatie/async#160, spatie/async#153, spatie/async#152, spatie/async#157, spatie/async#134, spatie/async#76, spatie/async#107, spatie/async#98, spatie/async#4.
• Removed global keyword usage, using static class Globals to maintain/passing child process GLOBALS like ext-parallel thread extension behaves.

3.1.1

• change Channel property names
• create standard I/O streams if missing instead of using the constants

3.1.0

• added kill() same as stop(), but different state status, for ext-parallel behavior
• update Channeled methods from self to static for proper usage when begin extended from, return type corrections
• status should not change on close() or stop()
• bug fix channel recv loop routine
• add indicator for Future being killed

3.0.5

test, refactor to allow passing globals between Futures as `ext-paral…

3.0.4

updates, have FutureInterface to include `Channel` api, allow channel…

3.0.3: corrections, refactor for better yield usage

- remove `spawn_setup` channel option to `setChannelTick` method
- refactor to allow channel `send/recv` run yield
- doc-block updates
- additional methods for tracking channels

doc-block corrections, simplify `parallel` closure setup, remove no longer needed function

3.0.2

Update Container.php