Using `rollup` to turn a tree of vat-defining source files into a bundle
object is somewhat slow. It seems to depend on the amount of code being
bundled: the worst case is the kernel sources, which take 1.5s . The kernel
needs a number of other vats which are automatically bundled at runtime. The
total process takes about 2.7s on my machine.

We have unit tests that run many swingsets in a single test file. The most
extreme case is test-message-patterns.js, which calls `buildVatController` 60
times in a row. It takes a really long time to run, 3-6 minutes, and the
majority is the bundling step. Parallelizing this doesn't help (JS is a
single-threaded language, it's not using non-blocking filesystem operations,
I don't know whether it's CPU or IO bound but either would be a problem).

This patch exports a new `buildKernelBundles()` function to let these
multi-swingset tests build the bundles once per test file. It also adds
`kernelBundles` to the `buildVatController(.., .., runtimeOptions)` options
bag to pass these bundles back in (with sensible defaults). The controller
gets all the built-in bundles from this collection, rather than running
`bundleSource` each time.

It also rearranges the console setup slightly, to make the `console` object
available earlier within `buildVatController`. I needed this to debug
problems with unpacking the other `runtimeOptions`. Also, now that we're
building our own `console` object, we no longer need to explicitly harden the
native console's (unique) prototype object.

refs #1643

To support `buildVatController(.., argv)`, the code modified the `config`
object (replacing `.parameters` on the bootstrap vat with the argv contents).
This mutation of the inbound `config` argument is a bit surprising, and
interferes with multi-swingset unit tests that might want to share the config
object among multiple `buildVatController` calls, or if the `config` object
is hardened.

This patch makes the controller build a new `config` object out of the pieces
of the original, with the new parameters overlaid on top.

Provides most of the fix to #1490 , but doesn't close it, since we still have
to think about `.devices`.

This changes test-message-patterns.js to build all vat bundles ahead of time,
once, in a `test.before()` clause, and shares both the bundles and the config
objects among all tests. This speeds up the overall test from 230s to 12s on
my machine.

It also removes lingering support for enabling/disabling pipelining, which I
needed when first implementing pipelining, but is now just in the way. And a
few noisy console.logs are gone.

We can achieve further speedups by amortizing bundling of the loopbox device
code, once the swingset config can accept device bundles in addition to
sourcePaths.

This now takes 6s, vs 22s before.

We can probably speed it up further by pre-bundling the test-specific vat
sources too.

This now takes 6s, vs 26s before.

This now takes 6s, vs 16s before.

I also removed the `copy(config)`, now that `buildVatController` no longer
mutates it.

We can probably speed it up further by pre-bundling the test-specific vat
sources too.