v0.8.4

ProbNumDiffEq v0.8.4

Diff since v0.8.3

Merged pull requests:

• Structure the tests into test groups (#177) (@nathanaelbosch)
• CompatHelper: bump compat for OrdinaryDiffEq to 6, (keep existing compat) (#182) (@github-actions[bot])
• Reduce allocations (#183) (@nathanaelbosch)
• CompatHelper: bump compat for OrdinaryDiffEq to 6, (keep existing compat) (#184) (@github-actions[bot])
• Test DiffEqDevTools.jl a bit better (#186) (@nathanaelbosch)
• Fix bug in the initialization via classic solvers (#187) (@nathanaelbosch)
• Run the benchmarks (#188) (@nathanaelbosch)