feature #38664 [RateLimiter] Moved classes implementing LimiterInterface to a new namespace (Nyholm)

This PR was squashed before being merged into the 5.2-dev branch.

Discussion
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[RateLimiter] Moved classes implementing LimiterInterface to a new namespace

| Q             | A
| ------------- | ---
| Branch?       | 5.x
| Bug fix?      | no
| New feature?  | no
| Deprecations? | no?
| Tickets       |
| License       | MIT
| Doc PR        |

Before we release the RateLimit component.
I think it would be a good idea to put the 7 classes that belongs to a specific strategy in their own "Policy" namespace. It is very likely that it will be more strategies in the future and the `Symfony\Component\RateLimiter` namespace is crowed as it is.

I decided not to put the `CompoundLimiter` in this namespace as it is not a strategy.

Commits
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1e6cea56e4 [RateLimiter] Moved classes implementing LimiterInterface to a new namespace

Author: fabpot

DependencyInjection/Configuration.php

@@ -31,7 +31,7 @@
 use Symfony\Component\Messenger\MessageBusInterface;
 use Symfony\Component\Notifier\Notifier;
 use Symfony\Component\PropertyInfo\PropertyInfoExtractorInterface;
-use Symfony\Component\RateLimiter\TokenBucketLimiter;
+use Symfony\Component\RateLimiter\Policy\TokenBucketLimiter;
 use Symfony\Component\Serializer\Serializer;
 use Symfony\Component\Translation\Translator;
 use Symfony\Component\Validator\Validation;
@@ -1843,7 +1843,7 @@ private function addRateLimiterSection(ArrayNodeDefinition $rootNode)
                                         ->info('The service ID of a custom storage implementation, this precedes any configured "cache_pool"')
                                         ->defaultNull()
                                     ->end()
-                                    ->enumNode('strategy')
+                                    ->enumNode('policy')
                                         ->info('The rate limiting algorithm to use for this rate')
                                         ->isRequired()
                                         ->values(['fixed_window', 'token_bucket', 'sliding_window', 'no_limit'])
@@ -1853,10 +1853,10 @@ private function addRateLimiterSection(ArrayNodeDefinition $rootNode)
                                         ->isRequired()
                                     ->end()
                                     ->scalarNode('interval')
-                                        ->info('Configures the fixed interval if "strategy" is set to "fixed_window" or "sliding_window". The value must be a number followed by "second", "minute", "hour", "day", "week" or "month" (or their plural equivalent).')
+                                        ->info('Configures the fixed interval if "policy" is set to "fixed_window" or "sliding_window". The value must be a number followed by "second", "minute", "hour", "day", "week" or "month" (or their plural equivalent).')
                                     ->end()
                                     ->arrayNode('rate')
-                                        ->info('Configures the fill rate if "strategy" is set to "token_bucket"')
+                                        ->info('Configures the fill rate if "policy" is set to "token_bucket"')
                                         ->children()
                                             ->scalarNode('interval')
                                                 ->info('Configures the rate interval. The value must be a number followed by "second", "minute", "hour", "day", "week" or "month" (or their plural equivalent).')