[3.x] Remove macros from InMemoryPage

[emmadesilva]

After #2548 I don't see the need for this any more. It's better to instead simply extend the class if needed. We do lose out on the internal typeLabel macro but it's not documented so I do not consider it part of BC. And we can instead set a good example by extracting thin wrapper classes.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (17f8ead) to head (dd98e88).

Additional details and impacted files

@@                       Coverage Diff                       @@
##             v3/redesign-in-memory-pages     #2550   +/-   ##
===============================================================
  Coverage                         100.00%   100.00%           
+ Complexity                          1744      1713   -31     
===============================================================
  Files                                179       175    -4     
  Lines                               4370      4295   -75     
===============================================================
- Hits                                4370      4295   -75     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.