[cleanup](build) Replace #include exec_env.h with forward declaration in 19 headers

[shuke987]

Summary

• Remove unused #include "runtime/exec_env.h" from 10 header files that don't reference ExecEnv
• Replace with class ExecEnv; forward declaration in 9 header files that only use ExecEnv* pointer
• Move full include to corresponding .cpp files where needed
• Add class Thread; forward declaration in workload_sched_policy_mgr.h (was transitively included via exec_env.h)

Files changed (24 files)

Headers - include removed (unused):

• exec/operator/aggregation_sink_operator.h
• exec/scan/scanner.h
• exec/sink/load_stream_map_pool.h
• exec/sink/load_stream_stub.h
• exec/sink/writer/vtablet_writer.h
• exec/sink/writer/vtablet_writer_v2.h
• load/group_commit/wal/wal_info.h
• storage/metadata_adder.h
• storage/rowset/rowset_writer_context.h
• storage/segment/page_handle.h

Headers - replaced with forward declaration:

• agent/workload_sched_policy_listener.h
• load/group_commit/group_commit_mgr.h
• load/group_commit/wal/wal_manager.h
• load/group_commit/wal/wal_table.h
• runtime/query_context.h
• runtime/workload_management/workload_sched_policy_mgr.h
• service/http/action/check_encryption_action.h
• service/http/action/compaction_score_action.h
• service/http/http_handler_with_auth.h

CPP files - added full include:

• agent/workload_sched_policy_listener.cpp
• load/group_commit/wal/wal_table.cpp
• runtime/workload_management/workload_sched_policy_mgr.cpp
• service/http/action/compaction_score_action.cpp
• service/http/http_handler_with_auth.cpp

Test plan

• Full BE compilation verified on build server
• CI buildall

🤖 Generated with Claude Code

[shuke987]

run buildall

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1. What problem was fixed (it's best to include specific error reporting information). How it was fixed.
2. Which behaviors were modified. What was the previous behavior, what is it now, why was it modified, and what possible impacts might there be.
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4. Which code was refactored and why was this part of the code refactored?
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