Refactor WiFi credential check; [Gen 4] WiFi thread safety issues, USB re-enumeration bugfix for weird USB hubs

[XuGuohui]

Problem

1. Device will save invalid credentials if there is valid crdentials with other SSID present
2. BLE provisioning breaks due to the Wi-Fi disconnection after setting credentials

Solution

1. Validate credentials before saving
2. Add a flag to not disconnect Wi-Fi connection after validating the credentials

Steps to Test

1. tests/wiring/wifi_cred_check
2. Go through BLE provisioning process

References

N/A

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Completeness

• User is totes amazing for contributing!
• Contributor has signed CLA (Info here)
• Problem and Solution clearly stated
• Run unit/integration/application tests on device
• Added documentation
• Added to CHANGELOG.md after merging (add links to docs and issues)

[XuGuohui]

@avtolstoy @jlovinger-particle This PR is ready for review now.

[Kategrode]

https://app.shortcut.com/particle/story/125680/add-wifi-credential-check

[Kategrode]

https://app.shortcut.com/particle/story/125195/device-os-5-7-0-breaks-serial-port-access-on-msom