Make built-in post-load callbacks public (#286)

[jtdub]

Summary

Closes #286.

The documented recipe for disabling a built-in post-load callback (Administrator Guide → Customizing Driver Rules) imported a private name — _remove_ipv4_acl_remarks — so an internal rename would silently break downstream drivers. This PR gives all eight built-in callbacks stable public identities, renamed in place in their driver modules:

Module	Public names
platforms/cisco_ios/driver.py	remove_ipv4_acl_remarks, remove_ipv6_acl_sequence_numbers (was _rm_...), add_acl_sequence_numbers
platforms/aruba_aoscx/driver.py	split_interface_vlan_trunk_allowed
platforms/cisco_xr/driver.py	fixup_xr_comments
platforms/hp_procurve/driver.py	fixup_hp_procurve_aaa_port_access (stutter fixed, was _fixup_..._fixup), fixup_hp_procurve_device_profile, fixup_hp_procurve_vlan

The docs recipe now removes by identity — rules.post_load_callbacks.remove(remove_ipv4_acl_remarks) — instead of slice-filtering against a private import.

Notes:

• Deliberately minimal per the issue: no remove_post_load_callback() helper, no __all__, no top-level re-exports (import from hier_config.platforms.<x>.driver, matching the existing split_vlan_id_lists precedent).
• Pure renames — behavior, signatures, and registration order unchanged. No deprecated aliases: the old names were private and v4 is unreleased.
• New tests: per-platform identity pins for all 8 callbacks (their imports double as rename regression guards) plus a recipe regression test proving removal keeps ACL remarks while the remaining callbacks still run.
• docs/dev/creating-drivers.md now tells future driver authors to use public callback names.

Self-Review Checklist

• poetry run ./scripts/build.py lint-and-test passes locally (lint + 95% test coverage).
• Tests were written first (TDD) and cover the change, following the testing conventions.
• CHANGELOG.md has an entry under ## [Unreleased] referencing this issue/PR ((#NNN)).
• Documentation is updated if public API or driver behavior changed (and mkdocs build --strict passes if docs were touched).
• Commit messages follow the contributing guide: imperative mood, subject ≤72 characters, body explains why.

AI-Assisted Contributions

Written with Claude Code; reviewed with the hier-config-review skill (no findings) and a four-angle cleanup pass (reuse/simplification/efficiency/altitude).