#35355 Use atomics for determining whether trace logging is enabled

Replaces the logging system's category-level maps and global log level with atomic bitmasks for debug and trace categories, making category enablement checks (`ShouldDebugLog` and `ShouldTraceLog`) inlined and lock-free. Incorporates changes from #34038 that replace `-loglevel` with a `-trace` command-line option and update the `logging` RPC to support trace categories with backward-compatible deprecation output. Also makes various logger configuration fields atomic or mutex-guarded to ensure thread safety without initialization ordering assumptions.

Problem: Checking whether trace or debug logging is active for a category requires map lookups or mutex acquisition, imposing CPU and lock overhead on hot multi-threaded code paths even when logging is disabled. Additionally, configuring trace logging previously required an unintuitive combination of `-debug` and `-loglevel` options.

Evidence of importance:

• PR description: 'simplify and optimize the logging-disabled path for LogTrace() ... reduces ShouldDebugLog and ShouldTraceLog to lock-free checks on a single atomic. Also makes Enabled() lock-free, to waste a little less time in the case where debugging is completely disabled.'
• Commit 0572c28fe3: 'This allows WillLogCategoryLevel to avoid taking a mutex, potentially allowing for better performance in the event that multiple threads are running many LogDebug(..) statements over categories that do not have -debug enabled (or LogTrace/-trace).'
• Commit 36586ec1b3: 'Simplifies the util/log.h API so that log enablement does not require indirection and ShouldDebugLog and ShouldTraceLog can be fully inlined at logging call sites.'

Scope: The PR is stacked on top of open PR #34038; the first three commits (replacing `-loglevel` with `-trace` and the RPC changes) belong to that base PR.

Risk of a mistake: medium (rpc_api, other). Modifications to logging startup parameters and the logging RPC output structure could break external management tooling and node automation scripts.

Changed since the previous assessment: Moved category bitmasks into static constinit atomics in util/log.h, enabling ShouldDebugLog and ShouldTraceLog to be fully inlined at call sites rather than relying on indirection through logger instances, and adapted the kernel logger accordingly.

Ready · Review #34038 first

Stacked on #34038; the base PR's changes are included in this diff.

Crickets

no substantive comment either way

Thread notes: Initial record. Draft PR opened by ajtowns with no reviewers or commenters yet.

Objections, suggestions, and questions: none recorded.

Depends on: #34038

Based on (shares commits with): #34038

215 lines under test/bench/ci.

• src/logging.cpp +47/-93
• src/logging.h +59/-62
• src/test/logging_tests.cpp +44/-59
• src/rpc/node.cpp +63/-24
• src/util/log.h +52/-14
• test/functional/feature_logging.py +37/-22
• src/init/common.cpp +23/-31
• src/kernel/bitcoinkernel.cpp +28/-11
• test/functional/rpc_misc.py +21/-8
• doc/release-notes-34038.md +13/-0
• src/test/i2p_tests.cpp +6/-4
• doc/developer-notes.md +4/-5
• src/bench/logging.cpp +3/-3
• test/functional/test_framework/test_node.py +4/-1
• src/test/util/setup_common.cpp +1/-2
• src/bitcoind.cpp +1/-1
• src/httpserver.cpp +1/-1
• src/node/abort.cpp +1/-1
• src/qt/guiutil.cpp +1/-1
• src/rpc/client.cpp +2/-0
• src/rpc/server.cpp +1/-1
• src/wallet/sqlite.cpp +1/-1
• src/init.cpp +0/-1
• src/init/common.h +0/-1

The short text the ranking pass compares across PRs.

This PR optimizes the disabled-logging path by replacing category log level maps and global levels with atomic bitmasks, making ShouldDebugLog and ShouldTraceLog fully inlined and lock-free across all threads. It also pulls in changes from #34038 that replace -loglevel with a -trace command-line flag and update the logging RPC with trace toggling and deprecation fallback. The changes eliminate lock contention when evaluating inactive log statements in hot multi-threaded code. It is currently in draft and depends on #34038.

P3 · speedup (ranking pass: Moved down to sit with #34038, on which it depends, and with the overlapping #35322.)

The PR makes disabled debug and trace category checks lock-free and fully inlined to eliminate mutex overhead on hot code paths. As stated in the description, it 'reduces ShouldDebugLog and ShouldTraceLog to lock-free checks on a single atomic' to avoid locking or map lookups across threads.

Membership: Directly refactors the logging subsystem in src/logging.cpp, src/logging.h, and src/util/log.h to use atomic bitmasks for categories.

Factors: security/stability 0, bug 0, performance 1, user value 1, leverage 0