Faster ParametersAcceptorSelector->combine()

[staabm]

the repro in phpstan/phpstan#8865 (comment) gets ~25% faster after this PR

1st call is before this PR
2nd call is after this PR

➜  spryker-phpstan-issue git:(master) ✗ php ../phpstan-src/bin/phpstan analyze --memory-limit=1G -l 5 src/Pyz/Zed/CategoryDataImport/Business/QueryExpander/FooQueryExpander.php --debug -vvv

Note: Using configuration file /Users/staabm/workspace/spryker-phpstan-issue/phpstan.neon.
Result cache not used because of debug mode.
/Users/staabm/workspace/spryker-phpstan-issue/src/Pyz/Zed/CategoryDataImport/Business/QueryExpander/FooQueryExpander.php
--- consumed 132 MB, total 164 MB, took 3.17 s
Result cache was not saved because only files were passed as analysed paths.

                                                                                                                        
 [OK] No errors                                                                                                         
                                                                                                                        

Used memory: 164 MB

➜  spryker-phpstan-issue git:(master) ✗ php ../phpstan-src/bin/phpstan analyze --memory-limit=1G -l 5 src/Pyz/Zed/CategoryDataImport/Business/QueryExpander/FooQueryExpander.php --debug -vvv

Note: Using configuration file /Users/staabm/workspace/spryker-phpstan-issue/phpstan.neon.
Result cache not used because of debug mode.
/Users/staabm/workspace/spryker-phpstan-issue/src/Pyz/Zed/CategoryDataImport/Business/QueryExpander/FooQueryExpander.php
--- consumed 132 MB, total 164 MB, took 2.66 s
Result cache was not saved because only files were passed as analysed paths.

                                                                                                                        
 [OK] No errors                                                                                                         
                                                                                                                        

Used memory: 164 MB

[ondrejmirtes]

Nice! Maybe this pattern (calling union in foreach instead of once) is in multiple places.