feat(sdk-core): optimize bulk accept share with adaptive batching

[aarvay]

Summary

This PR optimizes the bulk accept share request implementation by replacing the inefficient payload size calculation approach with smart adaptive batching that automatically discovers optimal batch sizes per coin type.

Context

The original PR (#6688) addressed the issue CSI-889 where users were getting 413 "Request Entity Too Large" errors when bulk accepting many wallet shares (78 in the reported case). However, the implementation had several inefficiencies:

• Built batches one item at a time with repeated payload size calculations
• Reduced the max payload size globally after failures, making all future batches unnecessarily small
• Didn't account for coin-specific key sizes (ETH keys are much larger than BTC keys)

Solution

This optimization implements an intelligent adaptive batching algorithm:

1. Optimistic First Attempt: Tries to send all shares at once (most requests will succeed)
2. Coin-Type Grouping: On 413 error, groups shares by coin type for efficient batching
3. Binary Search: Uses binary search to find the optimal batch size for each coin type
4. Memory: Remembers and reuses the optimal batch size for remaining items of the same coin
5. No Magic Numbers: No hardcoded batch sizes - automatically adapts to actual server limits

Key Benefits

• Efficient for mixed coins: ETH shares (large keys) can be sent 1-2 at a time while BTC shares (small keys) can be sent 20+ at a time
• Minimal API calls: Binary search quickly finds optimal batch sizes
• No unnecessary calculations: Removes all payload size calculations
• Self-adjusting: Automatically adapts to server limits without configuration

Testing

The existing tests should continue to pass as the external behavior remains the same - just more efficient internally.

Related

• Original PR: feat(sdk-core): add retry logic for bulk accept share requests #6688
• JIRA: CSI-889

To fix the problem, simply remove the assignment lastFailedSize = batch.length; on line 764, as it is never used and does not affect the control flow or logic of the function. No other changes are needed, and no imports or definitions are required. The fix is limited to the catch block inside the outer loop in the bulkAcceptShareRequestWithRetry method in modules/sdk-core/src/bitgo/wallet/wallets.ts.