feat(slic-stack.yml) control the WP_HTTP_BLOCK_EXTERNAL const

[lucatume]

Use the SLIC_WP_HTTP_BLOCK_EXTERNAL env var.

By default slic will set up the embedded WordPress installation to block all outgoing HTTP requests using the WP_HTTP_BLOCK_EXTERNAL constant.

In some instances this might cause issues with projects that need to call outside APIs to work.

This PR explores the possibility of controlling that constant value using the SLIC_WP_HTTP_BLOCK_EXTERNAL env var.

Similarly, this PR introduces control, via the .env.slic.run file, for the DISABLE_WP_CRON constant defined in the wp-config.php file.

[defunctl]

Tested with SLIC_WP_HTTP_BLOCK_EXTERNAL=false in my .env.slic.local and a slic restart now my plugin activation tests pass.

[defunctl]

Went into the WordPress docker container as well and ran a printenv to 100% confirm:

WORDPRESS_CONFIG_EXTRA=$scheme = empty( $_SERVER['HTTPS'] ) ? 'http' : 'https';
$url    = isset( $_SERVER['HTTP_HOST'] ) ? $_SERVER['HTTP_HOST'] : 'wordpress.test';
define( 'WP_HOME', $scheme . '://' . $url );
define( 'WP_SITEURL', $scheme . '://' . $url );
define( 'WP_REDIS_HOST', 'redis' );
define( 'WP_REDIS_PORT', 6379 );
define( 'TRIBE_NO_FREEMIUS', true );
define( 'WP_DEBUG_DISPLAY', true );
define( 'WP_DEBUG_LOG', true );
define( 'DISABLE_WP_CRON', true );
define( 'WP_HTTP_BLOCK_EXTERNAL', false );