Try memory leak workaround with zeroed mem

[brandonpayton]

What is this PR doing?

This PR attempts to fix the memory leak reported in #1128 and is an iteration on PR #1189 which had problems with "memory out of bounds" errors.

What problem is it solving?

It stops PHP from leaking memory throughout the runtime of a script and hopefully stops memory out of bounds errors by zeroing all memory given to PHP.

How is the problem addressed?

• By avoiding mmap()/munmap() which have incomplete implementations in Emscripten
• By using posix_memalign() to allocate memory instead and manually zeroing the memory before handing it to PHP

Testing Instructions

• Observe CI test results
• Use npm run dev and exercise Playground locally in the browser

[sejas]

@brandonpayton , Huge thanks for fixing this! It works great on NodeJS ❤️