nots/*: Поддержка пиров из pnpm.overrides (Experiment)

Конфигурирование, сборка, последующая работа показывает, что все работает, как задумано (в этом конкретном кейсе точно).

```
~/arcadia/devtools/dummy_arcadia/typescript/pnpm_overrides -nots-support-pnpm-overrides took 3s
at 15:29:04 f ❯ notsl build -- -n
Building devtools/dummy_arcadia/typescript/pnpm_overrides…
Warn[-WUserWarn]: in $S/devtools/frontend_build_platform/nots/builder/ya.make: Using branch nots/builder
Ok

~/arcadia/devtools/dummy_arcadia/typescript/pnpm_overrides -nots-support-pnpm-overrides took 6s
at 15:30:05 f ❯ notsl start

> @yandex-int/pnpm-overrides-demo@ start /Users/khoden/arcadia/devtools/dummy_arcadia/typescript/pnpm_overrides
> ya tool nots node build/index.js

from fake_lodash
Previous line should be 'from fake_lodash'
```
commit_hash:650c69f1fe38483cda5922ecd8cd813fffdf5bcd

1 files changed, 9 insertions, 4 deletions

diff --git a/build/plugins/lib/nots/package_manager/base/package_json.py b/build/plugins/lib/nots/package_manager/base/package_json.py
index 4fcb22e3ca..3840657992 100644
--- a/build/plugins/lib/nots/package_manager/base/package_json.py
+++ b/build/plugins/lib/nots/package_manager/base/package_json.py
@@ -1,9 +1,9 @@
 import json
+import logging
 import os
 
 from six import iteritems
 
-import logging
 from .utils import build_pj_path
 
 
@@ -19,7 +19,8 @@ class PackageJson(object):
     DEV_DEP_KEY = "devDependencies"
     PEER_DEP_KEY = "peerDependencies"
     OPT_DEP_KEY = "optionalDependencies"
-    DEP_KEYS = (DEP_KEY, DEV_DEP_KEY, PEER_DEP_KEY, OPT_DEP_KEY)
+    PNPM_OVERRIDES_KEY = "pnpm.overrides"
+    DEP_KEYS = (DEP_KEY, DEV_DEP_KEY, PEER_DEP_KEY, OPT_DEP_KEY, PNPM_OVERRIDES_KEY)
 
     WORKSPACE_SCHEMA = "workspace:"
 
@@ -93,12 +94,16 @@ class PackageJson(object):
 
     def dependencies_iter(self):
         for key in self.DEP_KEYS:
-            deps = self.data.get(key)
+            if key == self.PNPM_OVERRIDES_KEY:
+                deps = self.data.get("pnpm", {}).get("overrides", {})
+            else:
+                deps = self.data.get(key)
+
             if not deps:
                 continue
 
             for name, spec in iteritems(deps):
-                yield (name, spec)
+                yield name, spec
 
     def has_dependencies(self):
         first_dep = next(self.dependencies_iter(), None)