[Feat] Add ASU client and transport modules

[Fengli5355]

Purpose

This PR introduces the ASU client and transport modules under ucm/transport/kv/asu.

ASU provides an asynchronous KV transport layer between upper-level stores/connectors and different transport providers. It includes client-side routing and configuration, task lifecycle management, connection and buffer management, KV/SQE protocol handling, and transport provider abstraction.

This is the first PR of the feature_26h1 staged merge. kv-test, asu-store, connectors, and other upper-level modules will be merged in subsequent PRs.

Modifications

ASU module and client APIs

Add the ASU module skeleton, public client/transport APIs, configuration parsing, view management, and client-side routing.

Corresponding PR

• [Feat] Add ASU skeleton #962
• [Feat] Implementation of AsuClient. #967
• [Feat] Add initial async task manager for ASU #971
• [Feat] Add RouterConfig for AsuClient #1000
• [Opt] Move router to shared #1287

Client task management

Add asynchronous client task management, task completion handling, SPSC task queues, and single STORE/LOAD operations.

Corresponding PR

• [Feat] Refactor task management of AsuClient #1167
• [Feat] Refactor AsuClient task APIs #1182
• [Fix] Fix the logic of AsuClient Check. #1191
• [Refactor] Remove useless ClientBackend #1194
• [Refactor] Refine ASU task completion and pre-send failure handling #1229
• [Feat] Support ASU single STORE and LOAD protocols #1235
• [Refactor] Modify AsuClient task management #1240
• [Feat] Modify task datatype of AsuClient to spsc ring queue #1306

KV transport protocols

Add ASU KV/SQE protocols, request packing, submit flow, I/O scheduling, transport task execution, and response status handling.

Corresponding PR

• [Feat] Add ASU SQE protocol implementations #977
• [Feat] Implementation of BufferManager and KvProtocol. #991
• [Feat] Asu: add transport sub-batch foundation #997
• [Feat] Asu: build and send ASU SQE requests  #998
• [Feat] Asu: integrate submit flow with transport runtime  #999
• [Feat] Add VerifyPackedBuffer for all KV protocols #1002
• [Bugfix] Fix ASU SQE flag buffer calculation, send buffer default slots, and add debug/error logs. #1010
• [Fix][Opt]: Optimize status and memory release, refactor architecturefor asu_transport_impl. #1023
• [Opt] Simplify transport task finalization helpers #1034
• [Feat] ASU key field: 8-byte key in low 8B of 16B slot #1048
• [Feat] Use fixed 8-byte CacheKey instead of std::string #1056
• [Refactor] Improve ASU transport connection handling, task completion, and shutdown lifecycle #1173
• [Refactor] Consolidate and organize ASU client and transport tests #1202
• [Feat][Test] Refactor ASU buffer registration, unify QP config, and encapsulate task execution #1291
• [Opt] Optimize ASU transport performance with configurable backoff and reduced polling latency #1312

Connection and memory management

Add connection lifecycle management, endpoint recovery, buffer registration, shared transport providers, buffer-pool support, and memory-key propagation.

Corresponding PR

• [Feat] add connection manager #978
• [Refactor] Clean up ConnectionManager integration #988
• [Feat] Add RDMA memory registration to BufferManager #1014
• [Feat] use host-pinned memory with dual CPU/device addresses for transport buffers #1024
• [Feat] Adapt ASU client transport registration #1051
• [Feat] Unify ASU memory registration APIs and harden ASU transport registration and endpoint handling #1101
• [Feat] Trigger connection recovery after maxErrorCount consecutive failures #1171
• [Feat] Add TransProvider API GetServerCapabilities #1200
• [Feat] AsuTransports support shared provider #1222
• [Feat] Enable buffer pool support across runtime backends #1244
• [Opt] Refactor ASU memory key propagation through KVBuffer #1271
• [Opt] Replace acl in kv client with abstract runtime #1294

Transport providers

Add provider selection and integration for AICPU, externally supplied AIV libraries, and FakeBackend. Optimize concurrent FakeBackend task processing.

Corresponding PR

• [Feat] Add trans provider #1008
• [Feat] Wire TransProviderType::AIV to the static-library backend #1028
• [Feat] Add TransProvider API GetServerCapabilities #1200
• [Feat] AsuTransports support shared provider #1222
• [Opt] Asu fakebackend adds concurrent task processing in provider #1317

ASU-side integration APIs

Incorporate ASU-side API changes required by later kv-test, asu-store, and connector integration, without including those upper-level modules in this PR.

Corresponding PR

• [Feat] Asu store adaptation #1018
• [Feat] Adapt AsuStore to layerwise load/dump. #1031
• [Feat] Adapt kv-test transport runtime #1050
• [Feat] Adapt UCM connector to register KV cache regions #1127
• [Feat] AsuStore adds configurations of device_ip #1147
• [Feat] Support BufferPool and DramPool tests in simu backend #1175

Unit tests and build integration

Add ASU client and transport unit tests, reorganize the test suites, reduce test runtime, and enable ASU tests in CI.

Add the BUILD_UCM_ASU CMake option and wire the ASU module into the transport build.

Corresponding PR

• [Refactor] Consolidate and organize ASU client and transport tests #1202
• [Feat][Test] Refactor ASU buffer registration, unify QP config, and encapsulate task execution #1291
• [Opt] Asu unit tests speedup #1318

Test

Only ASU unit tests are required for this staged PR.
All unit tests passed.