Support ActiveRecord 7.2

[a-lavis]

1. Add Ruby 3.3 to CI
2. Set up CI / local dev to test multiple versions of ActiveRecord. Test 7.1 and 7.2 on CI.
3. Configure RSpec to use :focus metadata for ease of testing.
4. Update QueryCache tests for 7.2. We need to accomodate the changes in this commit: rails/rails@85742ce
   #query_cache used to return a Hash, but it now returns a custom class. Fortunately, both Hash and this custom class implement a #size method which works the same as doing keys.size.
5. Add with_connection_proxy method. ActiveRecord::Base now has the with_connection method, which is like the old connection method on ActiveRecord::Base but it yields the connection to a block instead of returning it: rails/rails@22f41a1
   This new method is now used for transactions, so in order for transactions to work we need to implement an equivalent in Replica Pools.

[amancevice]

looks good, but one minor change + question

[amancevice]

would it make more sense to make different groups instead of using ENV?

eg

group :rails7_1 do
  # ...
end

group :rails7_2 do
  # ...
end

[a-lavis]

The nice thing about the ENV variable is that we can set it to any version of ActiveRecord without having to update the Gemfile. But happy to switch it to this if you prefer!

[a-lavis]

With this diff:

diff --git a/Gemfile b/Gemfile
index 1c249f6..0170d9d 100644
--- a/Gemfile
+++ b/Gemfile
@@ -2,15 +2,21 @@ source "https://rubygems.org"
gemspec

group :development do
-  # This allows us to easily switch between different versions of ActiveRecord.
-  # To use this in local dev, you can do:
-  # ```
-  # rm Gemfile.lock
-  # ACTIVE_RECORD_VERSION="7.1" bundle install
-  # ```
-  active_record_version = ENV.fetch("ACTIVE_RECORD_VERSION", nil)
-  gem "activerecord", "~> #{active_record_version}.0" if active_record_version&.length&.positive?
-
  # Just helping out the bundler resolver:
  gem "rails", "> 6.0"
end
+
+# This allows us to easily switch between different versions of ActiveRecord.
+# To use this in local dev, you can do:
+# ```
+# rm Gemfile.lock
+# bundle config set --local with activerecord_7_1
+# bundle install
+# ```
+group :activerecord_7_1, optional: true do
+  gem "activerecord", "~> 7.1.0"
+end
+
+group :activerecord_7_2, optional: true do
+  gem "activerecord", "~> 7.2.0"
+end

after running:

rm Gemfile.lock
bundle install

I'm getting this error

[!] There was an error parsing `Gemfile`: You cannot specify the same gem twice with different version requirements.
You specified: activerecord (~> 7.1.0) and activerecord (~> 7.2.0). Bundler cannot continue.

 #  from /Users/aidanlavis/git/replica_pools/Gemfile:21
 #  -------------------------------------------
 #  group :activerecord_7_2, optional: true do
 >    gem "activerecord", "~> 7.2.0"
 #  end
 #  -------------------------------------------

Running:

bundle config set --local with activerecord_7_1

does not help