* Run tests in random order
Being able to run tests in any order is a pre-requisite for being able
to run them in parallel.
* Reset type coverage between tests, fix affected tests
* Reset parser and lexer between test runs and on php version change
Previously lexer was reset, but parser kept the reference to the old
one, and reference to the parser was kept by StatementsProvider. This
resulted in order-dependent tests - if the parser was first initialized
with phpVersion set to 7.4 then arrow functions worked fine, but were
failing when the parser was initially constructed with settings for 7.3
This can be demonstrated on current master by upgrading to
nikic/php-parser:4.9 and running:
```
vendor/bin/phpunit --no-coverage --filter="inferredArgArrowFunction" tests/ClosureTest.php
```
Now all tests using PHP 7.4 features must set the PHP version
accordingly.
* Marked more tests using 7.4 syntax
* Reset newline-between-annotation flag between tests
* Resolve real paths before passing them to checkPaths
When checkPaths is called from psalm.php the paths are resolved, so we
just mimicking SUT behaviour here.
* Restore newline-between-annotations in DocCommentTest
* Tweak Appveyor caches
* Tweak TravisCI caches
* Tweak CircleCI caches
* Run tests in parallel
Use `vendor/bin/paratest` instead of `vendor/bin/phpunit`
* Use default paratest runner on Windows
WrapperRunner is not supported on Windows.
* TRAVIS_TAG could be empty
* Restore appveyor conditional caching
This should make appveyor logs much more readable. Currently they have
thousands of lines like
```
Progress: Downloading php 7.4.3... 98%
Progress: Downloading php 7.4.3... 98%
Progress: Downloading php 7.4.3... 98%
```
