Merge bitcoin/bitcoin#30058: Encapsulate warnings in generalized node::Warnings and remove globals

260f8da71a refactor: remove warnings globals (stickies-v)
9c4b0b7ce4 node: update uiInterface whenever warnings updated (stickies-v)
b071ad9770 introduce and use the generalized `node::Warnings` interface (stickies-v)
20e616f864 move-only: move warnings from common to node (stickies-v)
bed29c481a refactor: remove unnecessary AppendWarning helper function (stickies-v)

Pull request description:

  This PR:
  - moves warnings from common to the node library and into the node namespace (as suggested in https://github.com/bitcoin/bitcoin/pull/29845#discussion_r1570069541)
  - generalizes the warnings interface to `Warnings::Set()` and `Warnings::Unset()` methods, instead of having a separate function and globals for each warning. As a result, this simplifies the `kernel::Notifications` interface.
  - removes warnings.cpp from the kernel library
  - removes warning globals
  - adds testing for the warning logic

  Behaviour change introduced:
  - the `-alertnotify` command is executed for all `KernelNotifications::warningSet` calls, which now also covers the `LARGE_WORK_INVALID_CHAIN` warning
  - the GUI is updated automatically whenever a warning is (un)set, covering some code paths where it previously wouldn't be, e.g. when `node::AbortNode()` is called, or for the `LARGE_WORK_INVALID_CHAIN` warning

  Some discussion points:
  - ~is `const std::string& id` the best way to refer to warnings? Enums are an obvious alternative, but since we need to define warnings across libraries, strings seem like a straightforward solution.~ _edit: updated approach to use `node::Warning` and `kernel::Warning` enums._

ACKs for top commit:
  achow101:
    ACK 260f8da71a
  ryanofsky:
    Code review ACK 260f8da71a. Only change since last review was rebasing
  TheCharlatan:
    Re-ACK 260f8da71a

Tree-SHA512: a3fcedaee0d3ad64e9c111aeb30665162f98e0e72acd6a70b76ff2ddf4f0a34da4f97ce353c322a1668ca6ee4d8a81cc6e6d170c5bbeb7a43cffdaf66646b588

src/node/interfaces.cpp

@@ -32,6 +32,7 @@
 #include <node/mini_miner.h>
 #include <node/transaction.h>
 #include <node/types.h>
+#include <node/warnings.h>
 #include <policy/feerate.h>
 #include <policy/fees.h>
 #include <policy/policy.h>
@@ -53,7 +54,6 @@
 #include <util/translation.h>
 #include <validation.h>
 #include <validationinterface.h>
-#include <warnings.h>
 
 #include <config/bitcoin-config.h> // IWYU pragma: keep
 
@@ -93,7 +93,7 @@ public:
     explicit NodeImpl(NodeContext& context) { setContext(&context); }
     void initLogging() override { InitLogging(args()); }
     void initParameterInteraction() override { InitParameterInteraction(args()); }
-    bilingual_str getWarnings() override { return Join(GetWarnings(), Untranslated("<hr />")); }
+    bilingual_str getWarnings() override { return Join(Assert(m_context->warnings)->GetMessages(), Untranslated("<hr />")); }
     int getExitStatus() override { return Assert(m_context)->exit_status.load(); }
     uint32_t getLogCategories() override { return LogInstance().GetCategoryMask(); }
     bool baseInitialize() override
@@ -101,6 +101,7 @@ public:
         if (!AppInitBasicSetup(args(), Assert(context())->exit_status)) return false;
         if (!AppInitParameterInteraction(args())) return false;
 
+        m_context->warnings = std::make_unique<node::Warnings>();
         m_context->kernel = std::make_unique<kernel::Context>();
         m_context->ecc_context = std::make_unique<ECC_Context>();
         if (!AppInitSanityChecks(*m_context->kernel)) return false;