Merge bitcoin/bitcoin#27661: doc, test: Document steps to reproduce TSan warning for libdb

f03a708 doc, test: Document steps to reproduce TSan warning for `libdb` (Hennadii Stepanov)

Pull request description:

  Requested [here](bitcoin/bitcoin#27658 (comment)).

ACKs for top commit:
  MarcoFalke:
    lgtm ACK f03a708

Tree-SHA512: 0c61c05d75d074df0686502739341fdbef8dd5a2d2f6cdfdd85bd0014ac43efb6fab112ee66d8d0f33f8f4695aeffc12a05923181260d81511d4e4d53b7686f2

Author: fanquake

test/sanitizer_suppressions/tsan

@@ -25,6 +25,7 @@ race:src/qt/test/*
 deadlock:src/qt/test/*
 
 # External libraries
+# https://github.com/bitcoin/bitcoin/pull/27658#issuecomment-1547639621
 deadlock:libdb
 race:libzmq