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.sw.approved.txt

@@ -10231,6 +10231,15 @@ with expansion:
 with message:
   Tested reporter: xml
 
+-------------------------------------------------------------------------------
+Reproducer for #2309 - a very long description past 80 chars (default console
+width) with a late colon : blablabla
+-------------------------------------------------------------------------------
+Reporters.tests.cpp:<line number>
+...............................................................................
+
+Reporters.tests.cpp:<line number>: PASSED:
+
 -------------------------------------------------------------------------------
 SUCCEED counts as a test pass
 -------------------------------------------------------------------------------
@@ -17030,6 +17039,6 @@ Misc.tests.cpp:<line number>
 Misc.tests.cpp:<line number>: PASSED:
 
 ===============================================================================
-test cases:  372 |  279 passed |  86 failed |  7 failed as expected
-assertions: 2131 | 1958 passed | 146 failed | 27 failed as expected
+test cases:  373 |  280 passed |  86 failed |  7 failed as expected
+assertions: 2132 | 1959 passed | 146 failed | 27 failed as expected