Limit get_accounts_by_authorizers results

[pur3miish]

Summary

• add a caller-supplied limit to get_accounts_by_authorizers
• enforce a node-side maximum of 1,000 results regardless of the requested limit
• stop traversing the account-query indices as soon as the effective limit is reached
• return more: true when matching authorities were truncated
• document the request and response fields in the Chain API schema
• add focused coverage for limited and complete result sets

Why

A public key can be assigned to an unusually large number of account permissions. The endpoint currently traverses and serializes every match, so a pathological or attacker-influenced authority set can consume significant CPU, memory, HTTP worker time, and bandwidth.

Applying a limit downstream does not protect nodeos because the complete response has already been generated. This change enforces the bound while iterating the node's authority index.

This addresses the node-side result-limit portion of #2417. Cursor pagination and cancellation-aware deadlines can be considered separately.

Validation

• git diff --check
• Chain API Swagger YAML parsed successfully with Ruby/Psych
• added get_accounts_by_authorizers_limit_test for truncated and complete results

The focused C++ test was not executed locally because this clean checkout does not include Leap's initialized submodules and pinned build toolchain; CI should compile and run it.

[pur3miish]

Superseded by the maintained Spring implementation: AntelopeIO/spring#1894. The corresponding Spring issue is AntelopeIO/spring#1893. Closing this draft because Leap is no longer supported.