Now the tool produces a far more readable output format, which bears a
lot of resemblance to YAML. In fact, the output should be machine
parseable as such, one document per testcase. However, the output format
may be subject to changes in future, so don't rely on this property.

In general, the output format has been optimized for producing a meaningful
textual diff, while keeping a decent readability as well. Therefore, not
everything is as compact as it could be, e.g. for an empty const pool we get:

    constant pool: [
    ]

instead of:

    constant pool: []

Also, trailing commas are always inserted in lists.

Additionally, now the tool accepts its output format as input. When
operating in this mode, all the snippets are extracted, processed and
the output is then emitted as usual. If nothing has changed, the output
should match the input. This is very useful for catching bugs in the
bytecode generation by running a textual diff against a known-good file.

The core (namely bytecode-expectations.cc) has been extracted from the
original cc file, which provides the utility as usual. The definitions
in the matching header of the library have been moved into the
v8::internal::interpreter namespace.

The library exposes a class ExpectationPrinter, with a method
PrintExpectation, which takes a test snippet as input, and writes the
formatted expectation to the supplied stream. One might then use a
std::stringstream to retrieve the results as a string and run it through
a diff utility.

BUG=v8:4280
LOG=N

Review URL: https://codereview.chromium.org/1688383003

Cr-Commit-Position: refs/heads/master@{#33997}