Make 7.5 compatible with the latest driver

[comandeo-mongo]

No description provided.

[Copilot]

Pull Request Overview

This pull request updates Mongoid 7.5 to be compatible with the latest MongoDB Ruby driver by updating compatibility matrices, dropping support for older Ruby and MongoDB versions, and fixing test infrastructure issues.

• Updates Ruby version support to require 2.6+ (dropping 2.5) and MongoDB support to 3.6-8.0 (dropping older versions)
• Replaces RSpec mocking implementation with direct method wrapping to fix Ruby 3.3 compatibility issues
• Updates test infrastructure and CI configuration to support newer driver and MongoDB versions

Reviewed Changes

Copilot reviewed 19 out of 19 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
spec/support/expectations.rb	Replaces RSpec mocking with direct method wrapping for query counting
spec/mongoid/query_cache_spec.rb	Adds MRI requirement and comments out session registry verification
spec/mongoid/criteria/queryable/extensions/fixnum_spec.rb	Updates describe block and adds Ruby version constraint
spec/mongoid/criteria/queryable/extensions/bignum_spec.rb	Updates describe block and adds Ruby version constraint
mongoid.gemspec	Updates Ruby version requirement and BSON dependency version range
docs/reference/compatibility.txt	Updates compatibility matrices for Ruby, MongoDB, and driver versions
README.md	Updates supported version ranges and copyright year
.github/workflows/test.yml	Updates CI matrix to test against MongoDB 8.0 and newer Ruby versions
.evergreen/*	Updates Evergreen CI configuration files for new test matrix

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