feat(ws): add subscribe_all_market for single-receiver all-event stream

[yovanoc]

Adds Client::subscribe_all_market(asset_ids) — returns Stream<Item = Result<WsMessage>> with all market event types from a single broadcast receiver.

Thin wrapper around subscribe_market_with_options(ids, true). Enables custom_feature_enabled.

Problem: calling multiple subscribe_* methods (orderbook + ltp + bba + tick_size + ...) creates N broadcast receivers on the same channel. Each gets a copy of every message. At 6+ receivers the broadcast overflows.

Fix: one call, one receiver, all events. Consumer dispatches by variant.

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Note

Medium Risk
Adds a new public subscription API that changes how consumers may multiplex market events; main risk is behavioral/compatibility issues around receiving and dispatching all WsMessage variants and ensuring the custom_feature_enabled flag is set as expected.

Overview
Adds Client::subscribe_all_market(asset_ids) to return a single Stream<Item = Result<WsMessage>> for all market channel events, using subscribe_market_with_options(..., true) to enable custom_feature_enabled and avoid multiple broadcast receivers.

Extends websocket tests to assert the subscription request includes "custom_feature_enabled":true and that the unified stream can receive both WsMessage::Book and WsMessage::BestBidAsk events.

^{Written by Cursor Bugbot for commit 40c28e2. This will update automatically on new commits. Configure here.}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.47%. Comparing base (8c98bb8) to head (40c28e2).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #292      +/-   ##
==========================================
+ Coverage   85.45%   85.47%   +0.02%     
==========================================
  Files          32       32              
  Lines        5121     5129       +8     
==========================================
+ Hits         4376     4384       +8     
  Misses        745      745              

Flag	Coverage Δ
rust	85.47% <100.00%> (+0.02%)	⬆️

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