Handle Data members that override __send__

[OskarEichler]

Summary

Dispatch Data member reads through the core send, preventing a member named send from shadowing the dispatcher.

Reproduction and verification

PP.singleline_pp(Data.define(:send, :other).new(1, 2), String.new) raises ArgumentError before this patch. The corpus also covers [], class, members, size and to_a. Existing private/removed-member cases remain green.

• Isolated branch: 6 focused checks pass under rbenv Ruby 4.0.6.
• Existing upstream RBENV_VERSION=4.0.6 rbenv exec rake test: 36 tests / 56 assertions, zero failures before and after.
• 2,000 ordinary single-/multi-line outputs remain byte-identical.
• Source-only change; no test files added or modified under the contributor's task constraint. Focused scripts are outside the repository. Other Ruby engines/versions and native Windows were not executed.

Breaking-change notes

No API removal. Data members named send now print successfully. Actual member accessors, including private ones, are still dispatched normally; existing handling of removed members is unchanged.