Add a pure RegressionReport service

[aliceinwire]

• Classifies regressions, fixes, unstable results, persistent failures, new results, and missing results.
• Preserves duplicate executions using occurrence indexes rather than collapsing them into dictionary entries.
• Uses origin, platform, architecture, compiler, configuration, path, and result type as the comparison identity.
• Incorporates Dashboard tree-report classifications for history-aware regression, fixed, and unstable detection.

[aliceinwire]

tested with the following script locally

KCI=(poetry run kci-dev)
GITURL=https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
BRANCH=master

mapfile -t commits < <(
  "${KCI[@]}" results summary \
    --giturl "$GITURL" \
    --branch "$BRANCH" \
    --history \
    --json |
    jq -r '(if type == "array" then . else .commits end)[0:2][].git_commit_hash'
)

HEAD=${commits[0]}
BASE=${commits[1]}

printf 'BASE=%s\nHEAD=%s\n' "$BASE" "$HEAD"

echo "#### compare"

"${KCI[@]}" results compare \
  --giturl "$GITURL" \
  --branch "$BRANCH" \
  --format json \
  "$BASE" "$HEAD" |
  jq .

echo "#### include-issues"

"${KCI[@]}" results compare \
  --giturl "$GITURL" \
  --branch "$BRANCH" \
  --include-issues \
  --format json \
  "$BASE" "$HEAD" |
  jq .

echo "#### gate"

"${KCI[@]}" results gate \
  --giturl "$GITURL" \
  --branch "$BRANCH" \
  --base "$BASE" \
  --head "$HEAD" \
  --fail-on regression \
  --format json |
  jq .

echo "#### gate latest"

"${KCI[@]}" results gate \
  --giturl "$GITURL" \
  --branch "$BRANCH" \
  --format json