(improv):support nested BSA and SBSA rule parsing

[Ashishsharma1903]

-add stack-based BSA/SBSA rule parsing to preserve nested subtests at any depth
-emit recursive subtests with sub_Test_Level and sub_Test_Path for log-aligned identity
-render nested BSA/SBSA subtests recursively in detailed HTML output
-apply BSA/SBSA subtest waivers recursively using sub_Test_Path, sub_Test_Number, legacy sub_Rule_ID, or description
-mark failed parent subtests as waived when all failed nested children are waived
-update log parser and waiver documentation for nested BSA/SBSA subtests

Signed-off-by: Ashish Sharma ashish.sharma2@arm.com
Change-Id: I3f7168156927d0abe81bd6ba50bca664c687dedc