Merge bitcoin/bitcoin#22001: doc: Generate doxygen documentation for test sources

5d37cc44f9 Generate doxygen documentation for test sources (Patrick Kamin)

Pull request description:

  Fixes #19248

  While searching for the documentation of the test utilities I realized they were excluded from doxygen. I agree with the statement in #19248. It's also helpful for new contributors to gain a broader understanding of the class dependencies visually (see BasicTestSetup)

ACKs for top commit:
  laanwj:
    ACK 5d37cc44f9

Tree-SHA512: 32f0abab2970c65621af5cee7f620c2653bd9688366e125543262bd078841e64a5a1e24cf0241e9f6ec538b8759e06108d5ff056449aa1c98d5f287deef18c86

doc/Doxyfile.in

@@ -863,9 +863,7 @@ RECURSIVE              = YES
 
 EXCLUDE                = src/crc32c \
                          src/leveldb \
-                         src/json \
-                         src/test \
-                         src/qt/test
+                         src/json
 
 # The EXCLUDE_SYMLINKS tag can be used to select whether or not files or
 # directories that are symbolic links (a Unix file system feature) are excluded