tools: add HTML test inventory generator for qcom-linux-testkit

Add a generator that scans Runner/suites for run.sh-based test suites and
builds a searchable HTML inventory page grouped by Area and Functional
Area.

Highlights:
- derive Area / Functional Area / Subarea / Test Case from suite paths
- link each test case name directly to the suite folder on GitHub
- summarize counts by Area and Functional Area
- show clearer PR-related metrics
- distinguish new suites in open PRs from updates to existing suites
- reduce noisy per-test PR mapping by limiting update tagging to
  suite-specific PRs

Signed-off-by: Srikanth Muppandam <smuppand@qti.qualcomm.com>

Author: smuppand