PHP8 - Adapter Signatures Compatibility

[michaeljoelphillips]

This PR takes a stab at the first item listed in #701 concerning PHP8 support.

What should be done about the missing constants on \ReflectionClassConstant for PHP < 8.0? In this PR I am declaring them on Roave\BetterReflection\Reflection\ReflectionClassConstant. I am assuming that the expectation for users on PHP7 will be to have some access to constants for the filter values, but I am open to feedback.

Since they are currently undocumented, here are the constants for reference:

php > $reflection = new ReflectionClass(ReflectionClassConstant::class);
php > var_dump($reflection->getConstants());
array(3) {
  ["IS_PUBLIC"]=>
  int(1)
  ["IS_PROTECTED"]=>
  int(2)
  ["IS_PRIVATE"]=>
  int(4)
}

[Ocramius]

Patch looks good, but we need to get rid of the design implications of core reflection API leaking into the new API: filtering logic should therefore be moved from the src/Reflection to the src/Reflection/Adapter logic, to avoid having ugly/complex logic like bitmask filtering exposed in the BC-compliant API.

[Ocramius]

Moved to 4.13.0. Reminder to self: change base branch after 4.12.0 is released

[michaeljoelphillips]

@Ocramius, I moved the filter logic to the adapter layer for both ReflectionClass and ReflectionObject and added tests. Thanks for the feedback.

[Ocramius]

@michaeljoelphillips can you expand on

BetterReflection/.github/workflows/phpunit.yml

Lines 17 to 27 in ecd6c1e

	strategy:
	matrix:
	dependencies:
	- "lowest"
	- "highest"
	- "locked"
	php-version:
	- "7.4"
	operating-system:
	- "ubuntu-latest"
	- "windows-latest"

to add php: 8.0 to it, perhaps?

[Ocramius]

LGTM 🚢

The addition of PHP 8.x to CI will happen separately, I suppose :-)

Thanks for the clarification comments and work on this, @michaeljoelphillips!