Merge #15201: net: Add missing locking annotation for vNodes. vNodes is guarded by cs_vNodes.

Summary:
eea02be70e Add locking annotation for vNodes. vNodes is guarded by cs_vNodes. (practicalswift)

Pull request description:

Add locking annotation for `vNodes`. `vNodes` is guarded by `cs_vNodes`.

Tree-SHA512: b1e18be22ba5b9dd153536380321b09b30a75a20575f975af9af94164f51982b32267ba0994e77c801513b59da05d923a974a9d2dfebdac48024c4bda98b53af

Backport of Core PR15201

Test Plan:

cmake -GNinja -DENABLE_WERROR=ON -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++ ..
ninja check check-functional

abc-p2p-avalanche is still failing for now, while the investigation continues

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Subscribers: deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D5690