Adopt XDR views: add differential test suites for ensuring byte-equal JSON responses #987

What

Each XDR-view migration swaps the decode-based path behind a v1 method for a view-walk over raw ledger bytes. The wire contract must not move and a client cannot tell the two backends apart. This issue tracks the differential suites that prove it, one per migrated method, by freezing the pre-view path test-locally and asserting it and the view path produce byte-identical response JSON over a corpus that sweeps the shapes the migration touches.

This should ensure byte equality, not semantic equality, so if a field appears, vanishes or reorders, the differential test suite fails.

• getTransactions (Adopt XDR views: migrate transaction read path to utilize XDR views #948 / Migrate transaction read path to use views #962): Add getTransactions differential test suite #976
• getEvents (Adopt XDR Views: View-based event filtering + response #950 / RPCv1 XDR views: migrate getEvents #978): Add getEvents differential tests #982

Acceptance criteria

• Add getTransactions differential test suite #976 merged: getTransactions suite plus the shared machinery in differential_test.go (generic comparator, cursor-chain driver, corpus builders, sqlite seeding).
• Add getEvents differential tests #982 merged: getEvents suite built on that machinery, with the SDK's GetEventsRequest.Matches frozen locally rather than called.
  • deprecate/remove unused legacy helpers in the SDK after
• Each suite's reference path is frozen in test code and no production code depends on it.
• Each suite pins its own corpus and filter table as non-vacuous, so a silently empty or one-shaped fixture cannot pass.
• Both suites pass and lint clean on feature/full-history once the stack lands.