Add missing oncall() declarations to soloader, conductor, and libpolarble BUCK files

Summary:
These BUCK files use fb_native rules that now enforce oncall via
_consume_oncall_and_feature. Without oncall() declarations, they
fail with "Missing oncall" errors.

- fbandroid/libraries/soloader: android_systems_reliability
- fbandroid/apps/study/libs/conductor: android_devxx
- fbandroid/.../libpolarble: milanda_mobile

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overriding_review_checks_triggers_an_audit_and_retroactive_review
Oncall Short Name: ar_engine_graphics

Differential Revision: D100111391

fbshipit-source-id: 9a35fcd5be1c5c7d5be1f9afc146eb2fa1bb19fd

Author: EricGriffith

BUCK

@@ -1,5 +1,7 @@
 load("//tools/build_defs/oss:soloader_defs.bzl", "android_aar", "export_file")
 
+oncall("android_systems_reliability")
+
 android_aar(
     name = "soloader",
     manifest_skeleton = "AndroidManifestSkeleton.xml",