Merge bitcoin#29892: test: Fix failing univalue float test

fa4c696 test: Fix failing univalue float test (MarcoFalke)

Pull request description:

  Currently the test may fail for some compilers, because `1e-8` may not be possible to represent exactly/consistently.

  ```
  $ ./src/univalue/test/object
  object: univalue/test/object.cpp:424: void univalue_readwrite(): Assertion `v.read("0.00000000000000000000000000000000000001e+30 ") && v.get_real() == 1e-8' failed.
  Aborted (core dumped)
  ```

  Fixes bitcoin#27256 (comment)

ACKs for top commit:
  laanwj:
    ACK fa4c696
  stickies-v:
    ACK fa4c696 , thanks for fixing!

Tree-SHA512: dea4f4f843381d5e8ffaa812b2290a11e081b29f8777d041751c4aa9942e60f1f8d2d1a652d9a52b41dec470a490c9fe26ca9bc762dd593c3521b328a8af2826

Author: fanquake

src/test/rpc_tests.cpp

@@ -291,6 +291,7 @@ BOOST_AUTO_TEST_CASE(rpc_parse_monetary_values)
     BOOST_CHECK_EQUAL(AmountFromValue(ValueFromString("1e-8")), COIN/100000000);
     BOOST_CHECK_EQUAL(AmountFromValue(ValueFromString("0.1e-7")), COIN/100000000);
     BOOST_CHECK_EQUAL(AmountFromValue(ValueFromString("0.01e-6")), COIN/100000000);
+    BOOST_CHECK_EQUAL(AmountFromValue(ValueFromString("0.00000000000000000000000000000000000001e+30")), 1);
     BOOST_CHECK_EQUAL(AmountFromValue(ValueFromString("0.0000000000000000000000000000000000000000000000000000000000000000000000000001e+68")), COIN/100000000);
     BOOST_CHECK_EQUAL(AmountFromValue(ValueFromString("10000000000000000000000000000000000000000000000000000000000000000e-64")), COIN);
     BOOST_CHECK_EQUAL(AmountFromValue(ValueFromString("0.000000000000000000000000000000000000000000000000000000000000000100000000000000000000000000000000000000000000000000000e64")), COIN);

src/univalue/test/object.cpp

@@ -421,7 +421,7 @@ void univalue_readwrite()
     // Valid, with leading or trailing whitespace
     BOOST_CHECK(v.read(" 1.0") && (v.get_real() == 1.0));
     BOOST_CHECK(v.read("1.0 ") && (v.get_real() == 1.0));
-    BOOST_CHECK(v.read("0.00000000000000000000000000000000000001e+30 ") && v.get_real() == 1e-8);
+    BOOST_CHECK(v.read("0.00000000000000000000000000000000000001e+30 "));
 
     BOOST_CHECK(!v.read(".19e-6")); //should fail, missing leading 0, therefore invalid JSON
     // Invalid, initial garbage