Merge bitcoin/bitcoin#30248: refactor: Add explicit cast to expected_last_page to silence fuzz ISan

fa9cb10 refactor: Add explicit cast to expected_last_page to silence fuzz ISan (MarcoFalke)

Pull request description:

  Fixes #30247

  I don't think this implicit cast can lead to any bugs, so make it explicit to silence the fuzz integer sanitizer.

  Can be tested with:

  ```
  FUZZ=wallet_bdb_parser UBSAN_OPTIONS="suppressions=$(pwd)/test/sanitizer_suppressions/ubsan:print_stacktrace=1:halt_on_error=1:report_error_type=1" ./src/test/fuzz/fuzz /tmp/1376869be72eebcc87fe737020add634b1a29533
  ```

  After downloading the raw fuzz input from https://github.com/bitcoin-core/qa-assets/blob/24c507b3ea6263e6b121fb8dced01123065c44c2/fuzz_seed_corpus/wallet_bdb_parser/1376869be72eebcc87fe737020add634b1a29533

ACKs for top commit:
  dergoegge:
    utACK fa9cb10

Tree-SHA512: 226dcc58be8d70b4eec1657f232c9c6648b5dac5eb2706e7390e65ce0a031fbaf8afce97d71a535c8294467dca4757c96f294d8cc03d5e6a1c0a036b0e070325

Author: fanquake

src/wallet/migrate.cpp

@@ -551,7 +551,7 @@ void BerkeleyRODatabase::Open()
     // }
 
     // Check the last page number
-    uint32_t expected_last_page = (size / page_size) - 1;
+    uint32_t expected_last_page{uint32_t((size / page_size) - 1)};
     if (outer_meta.last_page != expected_last_page) {
         throw std::runtime_error("Last page number could not fit in file");
     }