Sync fboss common.thrift into BGP OSS build via ShipIt pathmap

Summary:
BGP++'s OSS build (shipped to `github.com/facebook/BGP`) runs its own thrift compile of `rib_policy.thrift`, whose `include "configerator/structs/neteng/fboss/thrift/common.thrift"` (restored in the child diff, along with the `fboss_common.AllowSkipThriftCow` annotations) must resolve from BGP++'s OSS source root. The standalone getdeps build could not resolve it: FBOSS installs the compiled C++ for `common.thrift` (`common_types.h` under `include/`, symbols in `cfgr_fboss_common_cpp2`, both already consumed by BGP++) but not the raw `.thrift` schema.

`common.thrift` cannot be vendored as a repackaged copy the way BGP++'s other OSS schemas are. thrift-cow detects `AllowSkipThriftCow` by the annotation's resolved C++ type (`facebook::neteng::fboss::common::AllowSkipThriftCow`), which is derived from the thrift `package`, so keeping the package identical to FBOSS's is required for the annotation to be recognized. But a committed copy carrying that same `package` duplicates the implicit Thrift URI `facebook.com/neteng/fboss/common/AllowSkipThriftCow` already declared by the configerator source, which the land-blocking `thrift-duplicate-uri` linter rejects.

So this mirrors exactly what FBOSS does for the same file: sync the single configerator source into the OSS tree rather than committing a second copy.
- `manifests/bgp`: add a `[shipit.pathmap]` entry `fbcode/configerator/structs/neteng/fboss/thrift = configerator/structs/neteng/fboss/thrift` (matching `manifests/fboss`), so `getdeps` materializes `common.thrift` into BGP++'s OSS tree at fetch/ship time. The unrelated schemas in that dir are stripped so only `common.thrift` ships.
- `bgp_oss_build.bzl`: the `bgp-oss-build` CI builds from a staged `bgp_src/` (not from the pathmap), so stage `common.thrift` from the configerator source there too.

No file is committed under `public_tld`, so there is no duplicate URI and no `validate_cmake_sync` change is needed (`common.thrift` has no `add_fbthrift_cpp_library()` target; its C++ comes from `cfgr_fboss_common_cpp2`).

Replaces the previous version of this diff, which committed a vendored copy of `common.thrift` that tripped `thrift-duplicate-uri`. Per review feedback from joseph5wu (use the shipit option like FBOSS), this keeps the change on the BGP++ side and leaves FBOSS's install surface untouched.

Reviewed By: joseph5wu

Differential Revision: D111074394

fbshipit-source-id: 4802eeb380f44d2eb60867df03317a12ef21757b

Author: induvsuresh

build/fbcode_builder/manifests/bgp

@@ -32,6 +32,11 @@ gcc12
 fbcode/neteng/fboss/bgp/public_tld = .
 fbcode/neteng/fboss/bgp = neteng/fboss/bgp
 fbcode/fboss/common = common
+# common.thrift defines the @AllowSkipThriftCow annotation whose C++ type is
+# derived from its package, so rib_policy.thrift must resolve the exact FBOSS
+# schema. A committed copy under public_tld would duplicate the configerator
+# Thrift URI, so sync the real file in the same way manifests/fboss does.
+fbcode/configerator/structs/neteng/fboss/thrift = configerator/structs/neteng/fboss/thrift
 
 [shipit.strip]
 ^fbcode/neteng/fboss/bgp/.*facebook.*
@@ -44,3 +49,9 @@ fbcode/fboss/common = common
 ^fbcode/neteng/fboss/bgp/cpp/tests/NetlinkWrapperTest\.cpp
 ^fbcode/neteng/fboss/bgp/cpp/tests/PlatformConstantBbTest\.cpp
 ^fbcode/neteng/fboss/bgp/cpp/tests/FibEbbTest\.cpp
+# Only common.thrift is needed from configerator/structs/neteng/fboss/thrift;
+# strip the unrelated schemas the pathmap above would otherwise ship.
+^fbcode/configerator/structs/neteng/fboss/thrift/BUCK
+^fbcode/configerator/structs/neteng/fboss/thrift/package_versions\.thrift
+^fbcode/configerator/structs/neteng/fboss/thrift/platform_npi_stage\.thrift
+^fbcode/configerator/structs/neteng/fboss/thrift/sdk\.thrift