Fix bad indentation calculation in the console reporter

The problem came from the console reporter trying to provide a
fancy linebreaking (primarily for things like `SCENARIO` or the
BDD macros), so that new lines start with extra indentation if
the text being line broken starts as "{text}: ".

The console reporter did not properly take into account cases
where the ": " part would already be in a later line, in which
case it would ask for non-sensical level of indentation (larger
than single line length).

We fixed this by also enforcing that the special indentation case
only triggers if the ": " is found early enough in the line, so
that we also avoid degenerate cases like this:
```
blablabla: F
           a
           n
           c
           y
           .
           .
           .
```

Fixes #2309

tests/SelfTest/Baselines/console.std.approved.txt

@@ -1426,6 +1426,6 @@ due to unexpected exception with message:
   Why would you throw a std::string?
 
 ===============================================================================
-test cases:  372 |  295 passed |  70 failed |  7 failed as expected
-assertions: 2114 | 1958 passed | 129 failed | 27 failed as expected
+test cases:  373 |  296 passed |  70 failed |  7 failed as expected
+assertions: 2115 | 1959 passed | 129 failed | 27 failed as expected