feature #27648 [Lock] Added MongoDBStore (Joe Bennett)

This PR was merged into the 4.3-dev branch.

Discussion
----------

[Lock] Added MongoDBStore

| Q             | A
| ------------- | ---
| Branch?       | master
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes (requires `ext-mongodb` and `mongodb/mongodb` to test)
| Fixed tickets | #27345
| License       | MIT
| Doc PR        | symfony/symfony-docs#9807

**Testing caveat**
In order to test this, the test environment needs `ext-mongodb` and `mongodb/mongodb`.

I have both written the test and tested `Symfony\Component\Lock\Store\MongoDbStore` and it does pass in an environment with `ext-mongodb` and `mongodb/mongodb`.

**Description**
We should support Semaphore Locks with a MongoDB back end to allow those that already use MongoDB as a distributed storage engine.

Symfony already partially supports MongoDB for session storage: `Symfony\Component\HttpFoundation\Session\Storage\Handler\MongoDbSessionHandler`

**Example**

```php
$client = new MongoDb\Client();

$store = new Symfony\Component\Lock\Store\MongoDbStore(
    $client
    array(
        'database' => 'my-app',
    )
);
$lockFactory = new Symfony\Component\Lock\Factory($store);
$lock = $lockFactory->createLock('my-resource');
```

This is a squashed pull request of https://github.com/symfony/symfony/pull/27346

Commits
-------

9c04639dc3 #27345 Added Lock/Store/MongoDbStore

phpunit.xml.dist

@@ -19,6 +19,7 @@
         <env name="LDAP_PORT" value="3389" />
         <env name="REDIS_HOST" value="localhost" />
         <env name="MEMCACHED_HOST" value="localhost" />
+        <env name="MONGODB_HOST" value="localhost" />
         <env name="ZOOKEEPER_HOST" value="localhost" />
     </php>
 

src/Symfony/Component/Lock/composer.json

@@ -20,8 +20,9 @@
         "psr/log": "~1.0"
     },
     "require-dev": {
-        "predis/predis": "~1.0",
-        "doctrine/dbal": "~2.4"
+        "doctrine/dbal": "~2.4",
+        "mongodb/mongodb": "~1.1",
+        "predis/predis": "~1.0"
     },
     "autoload": {
         "psr-4": { "Symfony\\Component\\Lock\\": "" },

src/Symfony/Component/Lock/phpunit.xml.dist

@@ -12,6 +12,7 @@
         <ini name="error_reporting" value="-1" />
         <env name="REDIS_HOST" value="localhost" />
         <env name="MEMCACHED_HOST" value="localhost" />
+        <env name="MONGODB_HOST" value="localhost" />
         <env name="ZOOKEEPER_HOST" value="localhost" />
     </php>