Set memory limit for `composer phpcs` command

Problem/Motivation

The composer phpcs exceeds the php memory limit if it's 256MB or lower.

Steps to reproduce

Set memory limit to 256M and run composer phpcs:

The PHP_CodeSniffer "phpcs" command ran out of memory.
Either raise the "memory_limit" of PHP in the php.ini file or raise the memory limit at runtime
using `phpcs -d memory_limit=512M` (replace 512M with the desired memory limit).

Proposed resolution

Set memory limit to 512M for phpcs and phpcbf commands.

Remaining tasks

User interface changes

Introduced terminology

API changes

Data model changes

Release notes snippet