refactor: clear up blockstorage/streams in preparation for optimization

Made every OpenBlockFile#fReadOnly value explicit.

Replaced hard-coded values in ReadRawBlock with STORAGE_HEADER_BYTES.
Changed `STORAGE_HEADER_BYTES` and `UNDO_DATA_DISK_OVERHEAD` to `uint32_t` to avoid casts.

Also added `LIFETIMEBOUND` to the `AutoFile` parameter of `BufferedFile`, which stores a reference to the underlying `AutoFile`, allowing Clang to emit warnings if the referenced `AutoFile` might be destroyed while `BufferedFile` still exists.
Without this attribute, code with lifetime violations wouldn't trigger compiler warnings.

Co-authored-by: maflcko <6399679+maflcko@users.noreply.github.com>

src/streams.h

@@ -523,7 +523,7 @@ private:
     }
 
 public:
-    BufferedFile(AutoFile& file, uint64_t nBufSize, uint64_t nRewindIn)
+    BufferedFile(AutoFile& file LIFETIMEBOUND, uint64_t nBufSize, uint64_t nRewindIn)
         : m_src{file}, nReadLimit{std::numeric_limits<uint64_t>::max()}, nRewind{nRewindIn}, vchBuf(nBufSize, std::byte{0})
     {
         if (nRewindIn >= nBufSize)