Improvements 🔧

Improvements and bugfixes related to non-empty-string:
- Fix implode() for non-empty-string return type (phpstan/phpstan-src@520ae22), #5291
- Fixed encapsed string and concat operator in regard to non-empty-string (phpstan/phpstan-src@1283db7), #5301
- Fix inferring non-empty-string in array_map closure (phpstan/phpstan-src@b864a95), #5293
- Dynamic return type extension for functions that return non-empty-string when given one (phpstan/phpstan-src@4a9e069)
- str_pad() function return type extension (phpstan/phpstan-src@84503ce), #5307
- str_repeat() function return type extension (phpstan/phpstan-src@57d765f), #5307
- Cover non-empty-string in htmlentities() (#574) (#574), thanks @staabm!
- Cover non-empty-string in substr (#577), thanks @staabm!
DateTimeImmutable removed from DateTimeInterface results in DateTime (phpstan/phpstan-src@5eb96f5), #5259
Cover non-empty-array in array_combine (#578), thanks @staabm!
Cover non-empty-array in array_merge (#581), thanks @staabm!
Cover FileHelper methods with BC promise (phpstan/phpstan-src@4f9488e), #5306

Bugfixes 🐛

array_walk also understands object (#573), thanks @niconoe-!
Fix infinite recursion (phpstan/phpstan-src@8fd9667), #5231
Final Exception methods can never throw an exception (phpstan/phpstan-src@f5e88ae), #5299
Invalidating expressions without regexes (phpstan/phpstan-src@4220e43), #5129, #4970
Filter by falsey condition after the while loop (phpstan/phpstan-src@3166ba3), #5328, #5322

next() dynamic return type extension also valid for prev() (phpstan/phpstan-src@2fd7bfe
More array functions also accept object (phpstan/phpstan-src@a056d34)
Fix return type of Memcached::deleteMulti (#582), thanks @paulbalandan!