Move peer eviction tests to a separate test file

out of net_tests, because the eviction tests:

- are a different domain of test coverage, with different dependencies

- run more slowly than the net tests

- will be growing in size, in this PR branch and in the future, as eviction
  test coverage is improved

src/Makefile.test.include

@@ -101,6 +101,7 @@ BITCOIN_TESTS =\
   test/merkleblock_tests.cpp \
   test/miner_tests.cpp \
   test/multisig_tests.cpp \
+  test/net_peer_eviction_tests.cpp \
   test/net_tests.cpp \
   test/netbase_tests.cpp \
   test/pmt_tests.cpp \