…ars, fixing signaling and escaping (nicolas-grekas)

This PR was merged into the 3.3-dev branch.

Discussion
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[Process] Accept command line arrays and per-run env vars, fixing signaling and escaping

| Q             | A
| ------------- | ---
| Branch?       | master
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | yes
| Tests pass?   | yes
| Fixed tickets | #12488, #11972, #10025, #11335, #5759, #5030, #19993, #10486
| License       | MIT
| Doc PR        | -

I think I found a way to fix this network of issues once for all.
Of all the linked ones, only the last two are still open: the remaining were closed in dead ends.

Instead of trying to make `ProcessUtil::escapeArgument` work correctly on Windows - which is impossible as discussed in #21347 - this PR deprecates it in favor of a more powerful approach.

Depending on the use case:

- when a simple command should be run, `Process` now accepts an array of arguments (the "binary" being the first arg). Making this the responsibility of `Process` (instead of `ProcessBuilder`) gives two benefits:
  - escape becomes an internal detail that doesn't leak - thus can't be misused ([see here](#21347 (comment)))
  - since we know we're running a single command, we can prefix it automatically by "exec" - thus fixing a long standing issue with signaling

```php
        $p = new Process(array('php', '-r', 'echo 123;'));
        echo $p->getCommandLine();
        // displays on Linux:
        // exec 'php' '-r' 'echo 123;'
```

- when a shell expression is required, passing a string is still allowed. To make it easy and look-like sql prepared statements, env vars can be used when running the command. Since the shell is OS-specific (think Windows vs Linux) - this PR assumes no portability, so one should just use each shell's specific syntax.

From the fixtures:
```php
        $env = array('FOO' => 'Foo', 'BAR' => 'Bar');
        $cmd = '\\' === DIRECTORY_SEPARATOR ? 'echo !FOO! !BAR! !BAZ!' : 'echo $FOO $BAR $BAZ';
        $p = new Process($cmd, null, $env);
        $p->run(null, array('BAR' => 'baR', 'BAZ' => 'baZ'));

        $this->assertSame('Foo baR baZ', rtrim($p->getOutput()));
        $this->assertSame($env, $p->getEnv());
```

Commits
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330b61f [Process] Accept command line arrays and per-run env vars, fixing signaling and escaping