path: join refactor

Change variables init from var to let/const, added destructurization to function arguments and change old for to new for of

Local bench tests join

                                                                         confidence improvement accuracy (*)   (**)   (***)
 path/join-posix.js n=1000000 paths='/foo|bar||baz/asdf|quux|..'                         2.42 %       ±7.16% ±9.54% ±12.42%
 path/join-win32.js n=1000000 paths='C:\\\\foo|bar||baz\\\\asdf|quux|..'                -0.92 %       ±5.18% ±6.90%  ±8.98%

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• documentation is changed or added
• commit message follows commit guidelines