Apply improvements to performance testing setup in CI

[stevenbal]

Thema / Theme

Other

Omschrijving / Description

In open-zaak/open-zaak#2316 I made some changes to the setup for pytest-benchmark / bencher, to more easily track the performance on main in the bencher dashboard: https://bencher.dev/console/projects/open-zaak-ed2ce35-z71n5gf8t4f40/plots?back=L2NvbnNvbGUvb3JnYW5pemF0aW9ucy9vcGVuLXphYWstZWQyY2UzNS16NzFuNWdmOHQ0ZjQwL3Byb2plY3RzP3Blcl9wYWdlPTgmcGFnZT0x

Let's do the same for Objects API and also pin a plot on the dashboard to display the performance over time on master

Toegevoegde waarde / Added value

No response

Aanvullende opmerkingen / Additional context

No response