pw_env_setup: use latest versions of LUCI tools

Since LUCI tools aren't used in the Pigweed build, always grab the
latest versions of them. These tools are frequently updated but small
so bootstrap shouldn't take noticeably longer than before.

I went into pw_doctor to check that it didn't verify versions of the
LUCI tools and confirmed it does not. Added a comment clarifying this.

Also no longer get yapf from cipd. We never used that, we also got it
from pypi and we use that version. Also removing vpython, lucicfg, and
preview_email which were not used, and adding bb (the buildbucket
client).

Change-Id: I76850e3986dce498b7569573d4bf01b5a470779c

pw_doctor/py/pw_doctor/doctor.py

diff --git a/pw_doctor/py/pw_doctor/doctor.py b/pw_doctor/py/pw_doctor/doctor.py
index 8871810..7421c0a 100755
--- a/pw_doctor/py/pw_doctor/doctor.py
+++ b/pw_doctor/py/pw_doctor/doctor.py
@@ -196,6 +196,7 @@
         return  # This case is handled elsewhere.
 
     versions_path = root.joinpath('.cipd', 'pigweed', '.versions')
+    # Deliberately not checking luci.json--it's not required to be up-to-date.
     json_path = root.joinpath('pw_env_setup', 'py', 'pw_env_setup',
                               'cipd_setup', 'pigweed.json')
 

pw_env_setup/py/pw_env_setup/cipd_setup/luci.json

diff --git a/pw_env_setup/py/pw_env_setup/cipd_setup/luci.json b/pw_env_setup/py/pw_env_setup/cipd_setup/luci.json
index cc54c84..4e89470 100644
--- a/pw_env_setup/py/pw_env_setup/cipd_setup/luci.json
+++ b/pw_env_setup/py/pw_env_setup/cipd_setup/luci.json
@@ -2,56 +2,37 @@
     {
         "path": "infra/tools/luci/gerrit/${platform}",
         "tags": [
-            "git_revision:2155d0d436bf346333810cc352791063e1dda952"
+            "latest"
         ]
     },
     {
         "path": "infra/tools/luci/isolated/${platform}",
         "tags": [
-            "git_revision:2155d0d436bf346333810cc352791063e1dda952"
+            "latest"
         ]
     },
     {
         "path": "infra/tools/luci/led/${platform}",
         "tags": [
-            "git_revision:4799a3f4989e43e0dae5c35dfe5ce76cbdbb6125"
+            "latest"
         ]
     },
     {
         "path": "infra/tools/luci/logdog/logdog/${os}-${arch=amd64}",
         "tags": [
-            "git_revision:2155d0d436bf346333810cc352791063e1dda952"
+            "latest"
         ]
     },
     {
         "path": "infra/tools/luci-auth/${platform}",
         "tags": [
-            "git_revision:41a7e9bcbf18718dcda83dd5c6188cfc44271e70"
+            "latest"
         ]
     },
     {
-        "path": "infra/tools/luci/lucicfg/${platform}",
+        "path": "infra/tools/bb/${platform}",
         "tags": [
-            "git_revision:86afde8bddaefce47381b7cc4638b36717803d3a"
+            "latest"
         ]
-    },
-    {
-        "path": "infra/tools/luci/vpython/${platform}",
-        "tags": [
-            "git_revision:b01b3ede35a24f76f21420f11d13f234848e5d34"
-        ]
-    },
-    {
-        "path": "infra/tools/preview_email/${os}-${arch=amd64}",
-        "tags": [
-            "git_revision:2155d0d436bf346333810cc352791063e1dda952"
-        ]
-    },
-    {
-        "path": "infra/tools/yapf",
-        "tags": [
-            "git_revision:2155d0d436bf346333810cc352791063e1dda952"
-        ],
-        "_comment": "Keep in sync with tricium-recipes builder properties."
     }
 ]