Fixes #438

## What?

Removes the magic WordPress loading for the `wp-now php` command.

## Why?

It's not particularly intuitive that you get WordPress when you run
`wp-now php`. It's more intuitive that WordPress will load if you run
WP-CLI, so let's keep the behavior for that feature
(https://github.com/WordPress/wordpress-playground/issues/269).

## Testing Instructions

Tests should pass.

…395)

## What?

- Add the `executeWPCli` function to download and execute `wp-cli. 
- In the future, we may include the command `wp-now wp`. Currently, we
drop it out until we improve the pthreads execution. Currently a PR in
progress: #346
- Surface `emscriptenOptions` to catch print and print error for
`wp-cli` execution.

## Why?

- See https://github.com/WordPress/wordpress-playground/issues/269

## How?

It downloads the wp-cli.phar file if the file doesn't exist, then uses
`php.cli()` to execute it.
There are some limitations in the `wp-cli` features. Some of them may
not work.

## Testing Instructions

-  Check out this branch.
- Copy your path to your theme or plugin
- After installing and building the project, run:
- Run the tests `npx nx test wp-now`
- Observe the tests pass.

<!--details>
<summary>~`WP_NOW_PROJECT_PATH=/path/to/your-theme-or-plugin npx nx
preview wp-now wp user list`~ </summary>

```
> nx run wp-now:preview wp user list

+----+------------+--------------+--------------+--------------+---------------+
| ID | user_login | display_name | user_email   | user_registe | roles         |
|    |            |              |              | red          |               |
+----+------------+--------------+--------------+--------------+---------------+
| 1  | admin      | admin        | admin@localh | 2023-05-19 1 | administrator |
|    |            |              | ost.com      | 7:33:35      |               |
+----+------------+--------------+--------------+--------------+---------------+

  >  NX   Successfully ran target preview for project wp-now and 12 tasks it depends on (10s)
 
         With additional flags:
           wp user list
```
</details!-->

---------

Co-authored-by: Daniel Bachhuber <daniel.bachhuber@automattic.com>