depot_tools: add infra_paths recipe module for infra-specific paths

recipe_modules/bot_update/example.expected/tryjob_fail_patch.json

Index: recipe_modules/bot_update/example.expected/tryjob_fail_patch.json
diff --git a/recipe_modules/bot_update/example.expected/tryjob_fail_patch.json b/recipe_modules/bot_update/example.expected/tryjob_fail_patch.json
index c7a2976bc61723b8aa9e97c3aa7a524dfdd46871..d77b6b5d8ec581e0d781e83875b27d8374862501 100644
--- a/recipe_modules/bot_update/example.expected/tryjob_fail_patch.json
+++ b/recipe_modules/bot_update/example.expected/tryjob_fail_patch.json
@@ -25,7 +25,6 @@
       "--revision",
       "src@HEAD"
     ],
-    "cwd": "[SLAVE_BUILD]",
     "env": {
       "PATH": "%(PATH)s:RECIPE_PACKAGE_REPO[depot_tools]"
     },
@@ -67,7 +66,6 @@
       "-u",
       "import sys; sys.exit(1)"
     ],
-    "cwd": "[SLAVE_BUILD]",
     "name": "Patch failure",
     "~followup_annotations": [
       "step returned non-zero exit code: 1",