Cleanups output normalization in ApprovalTests

Removed:
 * NaN normalization
 * INFINITY normalization
 * errno normalization
 * Completely unused duration regex

Tests using these macros should be tagged `[approvals]`
so they are not run as part of approval tests.

Also simplified regex for the test's executable filename,
and hidden some tests relying on nullptr normalization.

tests/SelfTest/UsageTests/ToStringTuple.tests.cpp

@@ -38,8 +38,7 @@ TEST_CASE( "tuple<tuple<int>,tuple<>,float>", "[toString][tuple]" )
     CHECK( "{ { 42 }, { }, 1.2f }" == ::Catch::Detail::stringify(value) );
 }
 
-TEST_CASE( "tuple<nullptr,int,const char *>", "[toString][tuple]" )
-{
+TEST_CASE( "tuple<nullptr,int,const char *>", "[approvals][toString][tuple]" ) {
     typedef std::tuple<std::nullptr_t,int,const char *> type;
     type value { nullptr, 42, "Catch me" };
     CHECK( "{ nullptr, 42, \"Catch me\" }" == ::Catch::Detail::stringify(value) );