[infra] Restore pkg test coverage on analyzer builders

These were unintentionally removed in go/dart-reviews/335442.

Bug: b/310114753
Cq-Include-Trybots: luci.dart.try:analyzer-mac-release-try
Change-Id: I55e69fdef0acfe68fe0ade92a20fbc296e09f3a0
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/336900
Auto-Submit: Alexander Thomas <athom@google.com>
Commit-Queue: William Hesse <whesse@google.com>
Reviewed-by: William Hesse <whesse@google.com>

tools/bots/test_matrix.json

diff --git a/tools/bots/test_matrix.json b/tools/bots/test_matrix.json
index cd098de3..b4d2fa3 100644
--- a/tools/bots/test_matrix.json
+++ b/tools/bots/test_matrix.json
@@ -2572,10 +2572,11 @@
           ]
         },
         {
-          "name": "analyze co19 tests enable-asserts",
+          "name": "analyze co19 and pkg tests enable-asserts",
           "arguments": [
             "-nanalyzer-asserts-${system}",
-            "co19"
+            "co19",
+            "pkg"
           ]
         }
       ]