test: rename test suite name "tx_validationcache_tests" to match filename

Quoting src/test/README.md, 'Adding test cases':
    "The file naming convention is `<source_filename>_tests.cpp`
     and such files should wrap their tests in a test suite
     called `<source_filename>_tests`."

Currently the unit test source file txvalidationcache_tests.cpp contains a unit
test suite with the name tx_validationcache_tests, which is fixed by this commit.
The following shell script shows that this is the only mismatch and for all other
unit test source files the test suite names are correct:

 #!/bin/bash
 shopt -s globstar
 for test_full_filename in **/*_tests.cpp; do
     test_name_file=`basename $test_full_filename .cpp`
     test_name_suite=`sed -n "s/^.*TEST_SUITE(\(.*_tests\).*$/\1/p" $test_full_filename`
     if [ $test_name_file != $test_name_suite ]; then
         echo "TestFilename: $test_name_file != TestSuitname: $test_name_suite"
     fi
 done

Author: theStack

contrib/devtools/test_deterministic_coverage.sh

@@ -21,8 +21,8 @@ NON_DETERMINISTIC_TESTS=(
     "miner_tests/CreateNewBlock_validity"                     # validation.cpp: if (GetMainSignals().CallbacksPending() > 10)
     "scheduler_tests/manythreads"                             # scheduler.cpp: CScheduler::serviceQueue()
     "scheduler_tests/singlethreadedscheduler_ordered"         # scheduler.cpp: CScheduler::serviceQueue()
-    "tx_validationcache_tests/checkinputs_test"               # validation.cpp: if (GetMainSignals().CallbacksPending() > 10)
-    "tx_validationcache_tests/tx_mempool_block_doublespend"   # validation.cpp: if (GetMainSignals().CallbacksPending() > 10)
+    "txvalidationcache_tests/checkinputs_test"                # validation.cpp: if (GetMainSignals().CallbacksPending() > 10)
+    "txvalidationcache_tests/tx_mempool_block_doublespend"    # validation.cpp: if (GetMainSignals().CallbacksPending() > 10)
     "txindex_tests/txindex_initial_sync"                      # validation.cpp: if (GetMainSignals().CallbacksPending() > 10)
     "txvalidation_tests/tx_mempool_reject_coinbase"           # validation.cpp: if (GetMainSignals().CallbacksPending() > 10)
     "validation_block_tests/processnewblock_signals_ordering" # validation.cpp: if (GetMainSignals().CallbacksPending() > 10)

src/test/txvalidationcache_tests.cpp

@@ -15,7 +15,7 @@
 
 bool CheckInputScripts(const CTransaction& tx, TxValidationState &state, const CCoinsViewCache &inputs, unsigned int flags, bool cacheSigStore, bool cacheFullScriptStore, PrecomputedTransactionData& txdata, std::vector<CScriptCheck> *pvChecks);
 
-BOOST_AUTO_TEST_SUITE(tx_validationcache_tests)
+BOOST_AUTO_TEST_SUITE(txvalidationcache_tests)
 
 BOOST_FIXTURE_TEST_CASE(tx_mempool_block_doublespend, TestChain100Setup)
 {