High Confidence Buckets: Initial Release

Initial release of the High Confidence Buckets dataset along with
documentation describing how the data is derived and intended to be used
for Secure Boot DB and KEK 2023 certificate rollout.

This commit includes:
- The first published CSV set of high-confidence device buckets
- Background on bucket construction using SMBIOS identifiers
- Criteria for “high confidence” classification based on telemetry
- Intended usage by admins, OEMs, and non-Windows operating systems
- Dataset structure, schema, and data quality notes

The dataset enables transparent, auditable targeting of Secure Boot
certificate updates and allows ecosystem partners to replicate Microsoft’s
phased rollout logic.

Author: jgeurten