Rebalance telemetry_perf_unittest to other tests.

Continuing along with the attempt to rebalance test suites, up to
the 75th percentile, telemetry_perf_unittests still has nearly 3x
to 4x more overhead than chrome_public_test_apk and
content_browsertests. It also runs a lot faster. Looking at the numbers
in https://bugs.chromium.org/p/chromium/issues/detail?id=1021686#c12
and fudging it a little, we can reduce 3 shards of
telemetry_perf_unittest to slow down runs by about 23% without
making it into the long pole. We might be able to pull it down further
but variance in data makes it hard to fully reason about this.

These extra 3 shards can translate to 6-12 more shards of
chrome_public_test_apk of content_browsertests depending which
percentile you look at.

Making a guess, this will let us pick up 5 more content_browsertest
shards (this has lower overhead) and 3 more chrome_public_test_apks
shards.

Bug: 1021686
Change-Id: I7acf9db5d9ee2b2b33b366da0702b1658444d4f2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1922975
Auto-Submit: Albert J. Wong <ajwong@chromium.org>
Reviewed-by: Aaron Gable <agable@chromium.org>
Commit-Queue: Aaron Gable <agable@chromium.org>
Cr-Commit-Position: refs/heads/master@{#716894}

testing/buildbot/chromium.android.json

@@ -26647,7 +26647,7 @@
               "name": "shard #${SHARD_INDEX} logcats"
             }
           ],
-          "shards": 22
+          "shards": 25
         },
         "test": "chrome_public_test_apk"
       },
@@ -26828,7 +26828,7 @@
               "name": "shard #${SHARD_INDEX} logcats"
             }
           ],
-          "shards": 11
+          "shards": 16
         },
         "test": "content_browsertests"
       },
@@ -28863,7 +28863,7 @@
             }
           ],
           "idempotent": false,
-          "shards": 13
+          "shards": 10
         }
       }
     ],

testing/buildbot/test_suite_exceptions.pyl

@@ -327,7 +327,7 @@
       },
       'android-marshmallow-arm64-rel': {
         'swarming': {
-          'shards': 22,
+          'shards': 25,
         },
       },
       'KitKat Phone Tester (dbg)': {
@@ -448,7 +448,7 @@
       },
       'android-marshmallow-arm64-rel': {
         'swarming': {
-          'shards': 11,
+          'shards': 16,
         },
       },
       # chromium.linux
@@ -1622,7 +1622,7 @@
               'temp_band': '<30',
             },
           ],
-          'shards': 13,
+          'shards': 10,
         },
       },
       'android-pie-arm64-rel': {