Add PHP Dependencies

Adds PHP dependencies to bring the Unit Test images more inline with the extensions present on our LAMP stack.

$BUILD_DEPS unfortunately cannot be removed as the PHP extensions are dynamically not statically linked and need the libraries at runtime.

> ldd /usr/local/lib/php/extensions/no-debug-non-zts-20200930/bz2.so
        /lib/ld-musl-x86_64.so.1 (0x7febab0d1000)
        libbz2.so.1 => /usr/lib/libbz2.so.1 (0x7febab0ba000) <== This is part of bzip2-dev
        libc.musl-x86_64.so.1 => /lib/ld-musl-x86_64.so.1 (0x7febab0d1000)

This mostly resolves #17 (closed). There may be some apps that need special extensions, and we may eventually need to re-visit this, but this should resolve all current issues.