Caliptra Subsystem Gen 2.1.2 Release [1.val.doc]

Overview

Apply updates to release 2.1.2 for validation and documentation that do not modify the underlying RTL design.
Follows the release conventions in CaliptraSSReleaseChecklist.md and CaliptraReleaseChecklist.md for supporting collateral updates to patch releases.
Test cases are updated to resolve any regression failures, and documentation is updated with clarifications.

What's Changed

• [VAL] Cherry-pick regression fixes from main (PRs #817, #839, #844, #866, #882, #971, #992, #1008, #1141) by @calebofearth in #1136
• [DOC] Cherry-pick documentation updates from main (PRs: 922, 1011, 1012, 1125, 1129, 1143, 1144) by @calebofearth in #1149

Full Changelog: css-v2.1.2...css-v2.1.2+1.val.doc