[clang-format] Break long string literals in C#, etc.

Now strings that are too long for one line in C#, Java, JavaScript, and
Verilog get broken into several lines.  C# and JavaScript interpolated
strings are not broken.

A new subclass BreakableStringLiteralUsingOperators is used to handle
the logic for adding plus signs and commas.  The updateAfterBroken
method was added because now parentheses or braces may be required after
the parentheses or commas are added.  In order to decide whether the
added plus sign should be unindented in the BreakableToken object, the
logic for it is taken out into a separate function
shouldUnindentNextOperator.

The logic for finding the continuation indentation when the option
AlignAfterOpenBracket is set to DontAlign is not implemented yet.  So in
that case the new line may have the wrong indentation, and the parts may
have the wrong length if the string needs to be broken more than once
because finding where to break the string depends on where the string
starts.

The preambles for the C# and Java unit tests are changed to the newer
style in order to allow the 3-argument verifyFormat macro.  Some cases
are changed from verifyFormat to verifyImcompleteFormat because those
use incomplete code and the new verifyFormat function checks that the
code is complete.

The line in the doc was changed to being indented by 4 spaces, that is,
the default continuation indentation.  It has always been the case.  It
was probably a mistake that the doc showed 2 spaces previously.

Reviewed By: MyDeveloperDay

Differential Revision: https://reviews.llvm.org/D154093