BLE: improved pairing security

[hedger]

What's new

• ble: use unique root security keys for new pairings after pairing reset;
• ble: added migrations for existing pairing data;
• unit_tests: added migration tests

NB: Pairing information is upgraded to new format with this PR, it's not backwards compatible! Downgrading will lead to reset of BLE pairings.

Kudos to daw10 on Discord for providing report on potential security issues with old key usage model

Verification

• Upgrade to this branch, pairings from apps & main system should still work
• Check that keys file format is upgraded
• Reset pairing multiple times and validate that root keys stored at the start of pairing file are unique

Checklist (For Reviewer)

• PR has description of feature/bug or link to Confluence/Jira task
• Description contains actions to verify feature/bugfix
• I've built this code, uploaded it to the device and verified feature/bugfix

[github-actions]

Compiled f7 firmware for commit 6b02ca4f:

• 📦 Update package
• 📥 DFU file
• ☁️ Web/App updater
• 📊 Size report