refactor: fix missing includes

These cause compile failures with _LIBCPP_REMOVE_TRANSITIVE_INCLUDES.
i.e:
```bash
In file included from init.cpp:8:
./init.h:46:54: error: no template named 'atomic' in namespace 'std'
   46 | bool AppInitBasicSetup(const ArgsManager& args, std::atomic<int>& exit_status);
      |                                                 ~~~~~^
1 error generated.
```

See: https://libcxx.llvm.org/DesignDocs/HeaderRemovalPolicy.html.

src/crypto/sha256.cpp

@@ -7,8 +7,9 @@
 #include <crypto/sha256.h>
 #include <crypto/common.h>
 
-#include <assert.h>
-#include <string.h>
+#include <algorithm>
+#include <cassert>
+#include <cstring>
 
 #if !defined(DISABLE_OPTIMIZED_SHA256)
 #include <compat/cpuid.h>

src/init.h

@@ -6,9 +6,7 @@
 #ifndef BITCOIN_INIT_H
 #define BITCOIN_INIT_H
 
-#include <any>
-#include <memory>
-#include <string>
+#include <atomic>
 
 //! Default value for -daemon option
 static constexpr bool DEFAULT_DAEMON = false;