Merge bitcoin#18528: build: create test_fuzz library from src/test/fuzz/fuzz.cpp

691e2a7 build: create test_fuzz library from src/test/fuzz/fuzz.cpp (Harris)

Pull request description:

  This PR creates a static library **libtest_fuzz.a** to speed up the compilation of fuzz tests. It is functionally similar to bitcoin#17542

  Fixes bitcoin#18527

ACKs for top commit:
  MarcoFalke:
    ACK 691e2a7 🦁

Tree-SHA512: 39d7d2731ca4370db518dbb969eb17ddbf9c030c3fe0dec0d04ff6578f24a128563fe5aced78300c92ce296623a7079fea5aea70619819a20c56fb34191f00ef

Author: MarcoFalke

src/Makefile.am

@@ -725,6 +725,7 @@ include Makefile.leveldb.include
 endif
 
 include Makefile.test_util.include
+include Makefile.test_fuzz.include
 
 if ENABLE_TESTS
 include Makefile.test.include