[manipulation] Add UR3e model and TRI Homecart

This PR only contains a test that verifies that the model can be
parsed correctly (through model directives, etc). But in a follow-up
PR I will use this as a Drake example of bimanual motion planning with
Graph of Convex Sets.

These models were derived from the Anzu versions; with a few changes:
- Anzu has "left/right" variants of the ur3e models, which set tighter
joint limits for the homecart configuration.  I felt that it was a
little inelegant to put those in the ur3e directory (they should be
homecart specific).  We can add them later if need be.

- I've used the simple wsg gripper models that were already in Drake
instead of the fancier models in anzu.

- I've named the directory `tri_homecart` instead of `homecart`.

doc/_pages/model_version_control.md

@@ -27,12 +27,12 @@ See below for the suggested workflow.
 1. Clone ``RobotLocomotion/models`` locally
 2. Create a Git branch in your local checkouts of *both* ``models`` and
    ``drake``.
-3. Update ``drake/tools/workspace/models/repository.bzl`` to point to your
+3. Update ``drake/tools/workspace/models_internal/repository.bzl`` to point to your
    ``models`` checkout using
    ``github_archive(..., local_repository_override = <path>)``.
-4. Update ``drake/tools/workspace/models/files.bzl`` to incorporate the models
+4. Update ``drake/tools/workspace/models_internal/files.bzl`` to incorporate the models
    you want.
-5. Update ``drake/tools/workspace/models/package.BUILD.bazel`` to export the
+5. Update ``drake/tools/workspace/models_internal/package.BUILD.bazel`` to export the
    models.
 6. Ensure that you use ``forward_files`` to make the files available inside
    the Drake bazel workspace. For an example, see
@@ -42,7 +42,7 @@ See below for the suggested workflow.
 ## Submit Changes in a Pull Request
 
 1. Push your changes to your fork of ``RobotLocomotion/models``. Make a PR.
-2. Update ``drake/tools/workspace/models/models/repository.bzl`` to use the
+2. Update ``drake/tools/workspace/models_internal/repository.bzl`` to use the
    commit you pushed.
 3. Submit a PR to Drake, and add a self-blocking discussion thread, such as
    ``"Working temporary SHA1 until the models PR <LINK> is merged."``,
@@ -51,6 +51,6 @@ See below for the suggested workflow.
    request review for your ``models`` PR.
 5. Once both PRs are approved:
    1. Merge your ``models`` PR.
-   2. Update ``drake/tools/workspace/models/repository.bzl`` to the latest
+   2. Update ``drake/tools/workspace/models_internal/repository.bzl`` to the latest
       merge commit on ``master`` for ``RobotLocomotion/models``.
    3. Merge your ``drake`` PR.

manipulation/models/BUILD.bazel

@@ -12,6 +12,8 @@ install(
         "//manipulation/models/iiwa_description:install_data",
         "//manipulation/models/jaco_description:install_data",
         "//manipulation/models/realsense2_description:install_data",
+        "//manipulation/models/tri_homecart:install_data",
+        "//manipulation/models/ur3e:install_data",
         "//manipulation/models/wsg_50_description:install_data",
         "//manipulation/models/ycb:install_data",
     ],

manipulation/models/tri_homecart/BUILD.bazel

@@ -0,0 +1,59 @@
+# -*- python -*-
+
+load(
+    "@drake//tools/skylark:drake_cc.bzl",
+    "drake_cc_googletest",
+)
+load("//tools/install:install_data.bzl", "install_data")
+load("//tools/lint:lint.bzl", "add_lint_tests")
+load("@drake//tools/workspace/ros_xacro_internal:defs.bzl", "xacro_file")
+load("@drake//tools/workspace:forward_files.bzl", "forward_files")
+load("//tools/workspace/models_internal:files.bzl", "tri_homecart_mesh_files")
+
+# This package is public so that other packages can refer to
+# individual files in model from their bazel rules.
+package(
+    default_visibility = ["//visibility:public"],
+)
+
+# === test/ ===
+
+drake_cc_googletest(
+    name = "parse_homecart_test",
+    srcs = ["test/parse_homecart_test.cc"],
+    data = [
+        ":models",
+        "//manipulation/models/ur3e:models",
+        "//manipulation/models/wsg_50_description:models",
+    ],
+    deps = [
+        "//common:find_resource",
+        "//multibody/parsing",
+    ],
+)
+
+xacro_file(
+    name = "homecart_bimanual.urdf",
+    src = "homecart_bimanual.urdf.xacro",
+)
+
+xacro_file(
+    name = "homecart_cutting_board.sdf",
+    src = "homecart_cutting_board.sdf.xacro",
+)
+
+_TRI_HOMECART_MESHES = forward_files(
+    srcs = ["@models_internal//:" + x for x in tri_homecart_mesh_files()],
+    dest_prefix = "",
+    strip_prefix = "@models_internal//:tri_homecart/",
+    visibility = ["//visibility:private"],
+)
+
+install_data(
+    extra_prod_models = [
+        "homecart_bimanual.urdf",
+        "homecart_cutting_board.sdf",
+    ] + _TRI_HOMECART_MESHES,
+)
+
+add_lint_tests()

manipulation/models/tri_homecart/README.md

@@ -0,0 +1,7 @@
+# TRI HomeCart
+
+The HomeCart is a bimanual manipulation station developed at the Toyota
+Research Institute (TRI).  The model files contained here are all developed by TRI
+and distributed under Drake's license.  They represent a slightly simplified
+version of the model files used internally at TRI (most notably they are using
+a simplified version of the grippers). 

manipulation/models/tri_homecart/homecart.yaml

@@ -0,0 +1,5 @@
+directives:
+- add_directives:
+    file: package://drake/manipulation/models/tri_homecart/homecart_no_grippers.yaml
+- add_directives:
+    file: package://drake/manipulation/models/tri_homecart/homecart_grippers.yaml