[Feature Request]: Prepare release 3.x

[alexislefebvre]

Is your feature request related to a problem? Please describe.

Here is an open discussion to think about a new major version that would remove some features to help the maintenance and focus on the goal of this bundle: load fixtures.

• consider removing support of PHPCR:
  • it is a burden because it creates conflicts with dependencies, and it looks like the usage is very low
• consider removing the backups of database, they are broken: https://github.com/liip/LiipTestFixturesBundle/releases/tag/2.7.0
  • tests can randomly fail because generated backups are not consistent, see Improve phpunit configuration 2.x #109
• drop support of older dependencies:
  • PHP < 8.2 < 8.1
  • Symfony 5.4 this requirement hasn't been changed
  • drop old Doctrine dependencies if it can help issues with the last major versions, see feat: allow doctrine/orm 3, doctrine/dbal 4 (WIP) #265
  • remove the BC layers:
    • method_exists
    • search BC, in the code
• remove doctrine/annotations from the dependencies
• Document the changes in CHANGELOG (even though it's outdated), see [3.x][Doc] add upgrade guide for 3.x #301
• Add a note to README.md or the doc directory about the different versions of this bundle: a table with 1.x, 2.x and 3.x with their state, like this: https://github.com/DamienHarper/auditor?tab=readme-ov-file#version-information

Add support of Behat: load fixtures from a Behat scenario. But it may be added in a minor release later, if it doesn't require to break the bundle API.

Describe alternatives you've considered

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Additional context

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[alexislefebvre]

The 3.x branch has been created: https://github.com/liip/LiipTestFixturesBundle/tree/3.x

A lot of outdated lines has been removed: https://github.com/liip/LiipTestFixturesBundle/compare/2.x..3.x