SI-7969 REPL -C columnar output

Let `ConsoleReaderHelper.printColumns` print in a vertical
orientation (similar to `ls -C`) instead of horizontally (`ls -x`).

To support the old behavior, add a property `-Dscala.repl.format=across`
where "across" is the presumptive mnemonic for `-x`.

Extend column formatting to make columns only as wide as
their widest element. 

Example that really benefits, witness the skinny columns:

```
scala> math.

BigDecimal                     PartiallyOrdered             cosh      rint
BigInt                         Pi                           exp       round
E                              ScalaNumber                  expm1     signum
Equiv                          ScalaNumericAnyConversions   floor     sin
Fractional                     ScalaNumericConversions      hypot     sinh
IEEEremainder                  abs                          log       sqrt
Integral                       acos                         log10     tan
LowPriorityEquiv               asin                         log1p     tanh
LowPriorityOrderingImplicits   atan                         max       toDegrees
Numeric                        atan2                        min       toRadians
Ordered                        cbrt                         package   ulp
Ordering                       ceil                         pow
PartialOrdering                cos                          random

```