Improvement of VCL snippets management

[vrobert78]

To give the possibility to upload other VCL snippets than the default ones, we've refactored the code.
Instead of having all the snippet files in a single folder, they're now split into folders by snippet type.

So we can have multiple snippets for a given type.
This is also possible to set the snippet priority by setting it in the snippet name: "./recv/new_feature.10.vcl" will create a recv snippet for the new feature with priority 10.

[github-actions]

Thanks for the PR 😍

How to test these changes in your application

1. Add the Shopware flex endpoint in your composer.json to https://raw.githubusercontent.com/shopware/recipes/flex/pull-68/index.json.

   # When jq is installed
   jq '.extra.symfony.endpoint |= [ "https://raw.githubusercontent.com/shopware/recipes/flex/pull-68/index.json" ] + .' composer.json > composer.tmp && mv composer.tmp composer.json

   or manually

   "endpoint": [
       "https://raw.githubusercontent.com/shopware/recipes/flex/pull-68/index.json",
       "https://raw.githubusercontent.com/shopware/recipes/flex/main/index.json",
       "flex://defaults"
   ]

2. Install the package(s) related to this recipe:

   composer req 'shopware/fastly-meta:^6.4'

Diff between recipe versions

In order to help with the review stage, I'm in charge of computing the diff between the various versions of patched recipes.
I'm going keep this comment up to date with any updates of the attached patch.