feature #38565 [RateLimiter] Adding SlidingWindow algorithm (Nyholm)

This PR was squashed before being merged into the 5.x branch.

Discussion
----------

[RateLimiter] Adding SlidingWindow algorithm

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

This is a draft PR to make sure we like the idea. I'll keep working on adding tests.

Commits
-------

c6d3b70315 [RateLimiter] Adding SlidingWindow algorithm

Author: fabpot

DependencyInjection/Configuration.php

@@ -1817,14 +1817,14 @@ private function addRateLimiterSection(ArrayNodeDefinition $rootNode)
                                     ->enumNode('strategy')
                                         ->info('The rate limiting algorithm to use for this rate')
                                         ->isRequired()
-                                        ->values(['fixed_window', 'token_bucket'])
+                                        ->values(['fixed_window', 'token_bucket', 'sliding_window'])
                                     ->end()
                                     ->integerNode('limit')
                                         ->info('The maximum allowed hits in a fixed interval or burst')
                                         ->isRequired()
                                     ->end()
                                     ->scalarNode('interval')
-                                        ->info('Configures the fixed interval if "strategy" is set to "fixed_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 "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).')
                                     ->end()
                                     ->arrayNode('rate')
                                         ->info('Configures the fill rate if "strategy" is set to "token_bucket"')