move-only: Move SourceLocation to util/log.h

Introduce util/log.h as a lightweight header for code that only needs to emit
log messages. Move SourceLocation into this header so log-emitting code no
longer needs to include logging.h and depend on the full log management API.

This is a move-only change and the first change of several changes that
separate log generation from log handling. It also applies clang-format
suggestions to the moved code.

Review with --color-moved=dimmed-zebra --color-moved-ws=ignore-all-space

Co-authored-by: Ryan Ofsky <ryan@ofsky.org>

src/util/log.h

@@ -0,0 +1,32 @@
+// Copyright (c) The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_UTIL_LOG_H
+#define BITCOIN_UTIL_LOG_H
+
+#include <cstdint>
+#include <source_location>
+#include <string_view>
+
+/// Like std::source_location, but allowing to override the function name.
+class SourceLocation
+{
+public:
+    /// The func argument must be constructed from the C++11 __func__ macro.
+    /// Ref: https://en.cppreference.com/w/cpp/language/function.html#func
+    /// Non-static string literals are not supported.
+    SourceLocation(const char* func,
+                   std::source_location loc = std::source_location::current())
+        : m_func{func}, m_loc{loc} {}
+
+    std::string_view file_name() const { return m_loc.file_name(); }
+    std::uint_least32_t line() const { return m_loc.line(); }
+    std::string_view function_name_short() const { return m_func; }
+
+private:
+    std::string_view m_func;
+    std::source_location m_loc;
+};
+
+#endif // BITCOIN_UTIL_LOG_H