feat: provide message validation during extraction

[ramsey]

Description

This PR provides the --validate-messages option to the formatphp extract command. When providing this option, the CLI tool will respond with a non-zero exit code, if it encounters any errors, and it will also print all the errors to STDERR, like this:

Product requirements and context

How has this been tested?

PR Checklist

• I have added tests to cover my changes.

[ramsey]

I added a few extra folks to the reviewers list here, mainly to show y'all how this will work in lieu of having sniffs for source code linting of the message formatters on the PHP side.

When we run the extraction command, if there are validation errors, this is what devs will see (and we will run this command during the pre-commit hook, so it'll block if they have errors).

It will not check for style/convention issues (i.e., key names, enforced description, etc.) in the source code.

[qlty-cloud-legacy]

Code Climate has analyzed commit 156cb0c and detected 5 issues on this pull request.

Here's the issue category breakdown:

Category	Count
Complexity	5

The test coverage on the diff in this pull request is 100.0% (80% is the threshold).

This pull request will bring the total coverage in the repository to 96.9% (0.2% change).

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