Upgrade PHPBench to 1.7.0 and use aggregate-preview report

[dantleech]

This PR updates PHPBench to 1.7.0 and use the unstable "aggregate-preview" report (which may have minor changes prior to a 2.0 release). The "preview" report includes a diff column.

cc @staabm

[staabm]

lets give it a try, thank you @dantleech

[staabm]

@dantleech looking at the CI result in https://github.com/phpstan/phpstan-src/actions/runs/29727370175/job/88303447395 it seems the result table misses the "diff" column?

or maybe I need to regenerate the baseline for the new version?

[dantleech]

@staabm that run is prior to this PR being merged. I guess it's still runninng ... or .. I don't know 🤔

[dantleech]

ah the run conditions were not triggered:

on:
  pull_request:
    paths:
      - 'src/**'
      - '.github/workflows/bench.yml'
      - 'tests/bench/**'
  push:
    branches:
      - "2.2.x"
    paths:
      - 'src/**'
      - '.github/workflows/bench.yml'
      - 'tests/bench/**'