Deprecate ChiselStage$.elaborate as this exposes internal Chisel APIs,
namely "chisel3.internal.firrtl.Circuit".  Replace usages of this in
tests with emitCHIRRTL.

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@sifive.com>

* Change many tests from simulation-based to checking the CHIRRTL.
* Move tests that were hard to convert to new VecIntegrationSpec in
  integration-tests

Co-authored-by: Jack Koenig <koenig@sifive.com>

* mdoc-ify intrinsic explanation

* Update docs/src/explanations/intrinsics.md

* Update intrinsics.md

* IntModule

* intmodule works

* a bit of documentation

* formatting

* example and better test.  Rename all the things, now they are Blue!

* formatting

* typo

* move file

* indexes

* Update core/src/main/scala/chisel3/internal/firrtl/IR.scala

Co-authored-by: Schuyler Eldridge <schuyler.eldridge@gmail.com>

* Update docs/src/explanations/intrinsics.md

Co-authored-by: Schuyler Eldridge <schuyler.eldridge@gmail.com>

* Update docs/src/explanations/intrinsics.md

Co-authored-by: Schuyler Eldridge <schuyler.eldridge@gmail.com>

* simplify tests

---------

Co-authored-by: Schuyler Eldridge <schuyler.eldridge@gmail.com>

Change FIRRTL Circuit conversion/serialization to place
ChiselAnnotations (converted to FIRRTL Annotations) inside the FIRRTL
Circuit and to serialize this using the "%[[]]" inline JSON format that
is present in the FIRRTL spec.  This does not remove _all_ annotations
passed via the annotation file, but it is the first step towards that.

* Add low-level svsim based simulation to Chisel
* Add Peek/Poke API

Introduce `svsim`, a low level library for simulating SystemVerilog using Verilator and VCS. (#3121)

Also run formatting on SBT files.

Directly subclassing Iterable is lazy-ish, but if you call any operation
on the resulting value (eg. map or ++) it will evaluate the Iterable and
return a List.

Co-authored-by: Jack Koenig <koenig@sifive.com>
Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

Use new private Record._elements to validate Record elements. This
allows us to check invariants earlier than on cloning or binding.

It seems that deprecations on methods that are macro expanded away do
not actually trigger a deprecation warning. Instead, we will just accept
no source locator on the deprecated API (no released version of Chisel
has the source locator).