Update Curl is_resource() to work with PHP 8 CurlHandle and CurlMultiHandle objects

[Ayesh]

Updates is_resource() calls for curl handlers to properly work with PHP 8's \CurlHandle and \CurlMultiHandle objects.
See https://php.watch/versions/8.0/resource-CurlHandle

PHPDoc comments are updated to indicate that the variable/property can be either a resource or a Curl object.
In PHP 8, curl_close() calls are no-op, and and explicit unset() call is added to ensure the \CurlHandle object is destroyed.

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This PR depends on #2714 (to enable tests).
Related: #2702

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On manual/forced PHP 8 tests, there are two failures related to this repo (and 10 errors related to promises).

There were 2 failures:

1) GuzzleHttp\Test\Handler\CurlFactoryTest::testCreatesCurlHandle
Failed asserting that CurlHandle Object &00000000184dcf9b000000006cc08298 () is of type "resource".

##[error]/home/runner/work/guzzle/guzzle/tests/Handler/CurlFactoryTest.php:49

2) GuzzleHttp\Test\Handler\CurlFactoryTest::testEmitsProgressToFunction
Failed asserting that actual size 5 matches expected size 4.

##[error]/home/runner/work/guzzle/guzzle/tests/Handler/CurlFactoryTest.php:289

ERRORS!
Tests: 486, Assertions: 2092, Errors: 10, Failures: 2, Skipped: 5.

This PR fixes the two failures related to this repo:

Tests: 486, Assertions: 2120, Errors: 10, Skipped: 5.

[Nyholm]

Could you make sure we test this on php8 too?

[GrahamCampbell]

PHP 8 is pending #2712 first, to avoid conflicts and to ensure the dependencies work on PHP 8.

[GrahamCampbell]

This needs rebasing. :)

[Nyholm]

I'll be happy to merge this once you rebase it and the CI is green

[Ayesh]

Thank you @Nyholm and @GrahamCampbell - I just force-pushed after rebasing from current master branch.

[Nyholm]

Could you also make sure the CI is green?

[Ayesh]

Both test failures are due to the PHP 8's changes in parameter types. I suppose both static analyzers infer the parameter types via Reflection.

It wouldn't be ideal if we were to make psalm/phpstan suppress these errors, but that's the only approach I can think of for now. Even if were to run the static analyzers on PHP 8, it would now complain about the other type of parameters too.

[Ayesh]

I will make changes in psalm/phpstan config files so it ignores the type mismatch false positives.

[Nyholm]

I agree with you. Let's update the baselines for now.

[Ayesh]

Thanks for updating the baselines, it wasn't something I had a lot of experience.

[Nyholm]

I ran the following commands:

phpstan analyze  --generate-baseline
psalm --set-baseline=psalm.baseline.xml

[Nyholm]

Thank you for your work and for the reviews

[mfn]

I ran the following commands:

phpstan analyze  --generate-baseline
psalm --set-baseline=psalm.baseline.xml

I was about to suggest to add this to composer.json scripts but then realized neither phpstan/psalm is actually a dev dependency, so that would be odd.

This could be unnecessary friction for newcomers, can't expect everyone to know the ins/outs of all the tools I guess, at least when it comes to handling things like updating the baseline.

Any ideas how to make this easier? 🤔

[Nyholm]

Running these commands are rare. Newcomers will never run this.