Merge bitcoin/bitcoin#27636: kernel: Remove util/system from kernel library, interface_ui from validation.

7d3b35004b refactor: Move system from util to common library (TheCharlatan)
7eee356c0a refactor: Split util::AnyPtr into its own file (TheCharlatan)
44de325d95 refactor: Split util::insert into its own file (TheCharlatan)
9ec5da36b6 refactor: Move ScheduleBatchPriority to its own file (TheCharlatan)
f871c69191 kernel: Add warning method to notifications (TheCharlatan)
4452707ede kernel: Add progress method to notifications (TheCharlatan)
84d71457e7 kernel: Add headerTip method to notifications (TheCharlatan)
447761c822 kernel: Add notification interface (TheCharlatan)

Pull request description:

  This pull request is part of the `libbitcoinkernel` project https://github.com/bitcoin/bitcoin/issues/27587 https://github.com/bitcoin/bitcoin/projects/18 and more specifically its "Step 2: Decouple most non-consensus code from libbitcoinkernel".

  ---

  It removes the kernel library's dependency on `util/system` and `interface_ui`. `util/system` contains networking and shell-related code that should not be part of the kernel library. The following pull requests prepared `util/system` for this final step: https://github.com/bitcoin/bitcoin/pull/27419 https://github.com/bitcoin/bitcoin/pull/27254 https://github.com/bitcoin/bitcoin/pull/27238.

  `interface_ui` defines functions for a more general node interface and has a dependency on `boost/signals2`. After applying the patches from this pull request, the kernel's reliance on boost is down to `boost::multiindex`.

  The approach implemented here introduces some indirection, which makes the code a bit harder to read. Any suggestions for improving or reworking this pull request to make it more concise, or even reworking it into a more proper interface, are appreciated.

ACKs for top commit:
  MarcoFalke:
    re-ACK 7d3b35004b (no change) 🎋
  stickies-v:
    Code Review ACK 7d3b35004b
  hebasto:
    re-ACK 7d3b35004b, only last two commits dropped since my [recent](https://github.com/bitcoin/bitcoin/pull/27636#pullrequestreview-1435394620) review.

Tree-SHA512: c8cfc698dc9d78e20191c444708f2d957501229abe95e5806106d1126fb9c5fbcee686fb55645658c0107ce71f10646f37a2fdf7fde16bbf22cbf1ac885dd08d

src/test/fuzz/integer.cpp

@@ -4,6 +4,7 @@
 
 #include <arith_uint256.h>
 #include <common/args.h>
+#include <common/system.h>
 #include <compressor.h>
 #include <consensus/amount.h>
 #include <consensus/merkle.h>
@@ -32,7 +33,6 @@
 #include <util/overflow.h>
 #include <util/strencodings.h>
 #include <util/string.h>
-#include <util/system.h>
 #include <version.h>
 
 #include <cassert>

src/test/fuzz/string.cpp

@@ -5,6 +5,7 @@
 #include <blockfilter.h>
 #include <clientversion.h>
 #include <common/args.h>
+#include <common/system.h>
 #include <common/url.h>
 #include <netbase.h>
 #include <outputtype.h>
@@ -24,7 +25,6 @@
 #include <util/settings.h>
 #include <util/strencodings.h>
 #include <util/string.h>
-#include <util/system.h>
 #include <util/translation.h>
 
 #include <cassert>

src/test/fuzz/system.cpp

@@ -55,7 +55,7 @@ FUZZ_TARGET_INIT(system, initialize_system)
             [&] {
                 const OptionsCategory options_category = fuzzed_data_provider.PickValueInArray<OptionsCategory>({OptionsCategory::OPTIONS, OptionsCategory::CONNECTION, OptionsCategory::WALLET, OptionsCategory::WALLET_DEBUG_TEST, OptionsCategory::ZMQ, OptionsCategory::DEBUG_TEST, OptionsCategory::CHAINPARAMS, OptionsCategory::NODE_RELAY, OptionsCategory::BLOCK_CREATION, OptionsCategory::RPC, OptionsCategory::GUI, OptionsCategory::COMMANDS, OptionsCategory::REGISTER_COMMANDS, OptionsCategory::HIDDEN});
                 // Avoid hitting:
-                // util/system.cpp:425: void ArgsManager::AddArg(const std::string &, const std::string &, unsigned int, const OptionsCategory &): Assertion `ret.second' failed.
+                // common/args.cpp:563: void ArgsManager::AddArg(const std::string &, const std::string &, unsigned int, const OptionsCategory &): Assertion `ret.second' failed.
                 const std::string argument_name = GetArgumentName(fuzzed_data_provider.ConsumeRandomLengthString(16));
                 if (args_manager.GetArgFlags(argument_name) != std::nullopt) {
                     return;
@@ -64,7 +64,7 @@ FUZZ_TARGET_INIT(system, initialize_system)
             },
             [&] {
                 // Avoid hitting:
-                // util/system.cpp:425: void ArgsManager::AddArg(const std::string &, const std::string &, unsigned int, const OptionsCategory &): Assertion `ret.second' failed.
+                // common/args.cpp:563: void ArgsManager::AddArg(const std::string &, const std::string &, unsigned int, const OptionsCategory &): Assertion `ret.second' failed.
                 const std::vector<std::string> names = ConsumeRandomLengthStringVector(fuzzed_data_provider);
                 std::vector<std::string> hidden_arguments;
                 for (const std::string& name : names) {