scripted-diff: net: rename permissionFlags to permission_flags

Summary:

-BEGIN VERIFY SCRIPT-
sed -i 's/permissionFlags/permission_flags/g' $(git grep -l permissionFlags)
-END VERIFY SCRIPT-

This is a partial backport of core#25962
https://github.com/bitcoin/bitcoin/pull/25962/commits/377e9ccda469731d535829f184b70c73ed46b6ef

Depends on D17110

Test Plan: ninja all check-all

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D17111