Update Node to include 25/26 (and remove 20/22) and Deno to a modern version (2.8.3).

[vbudovski]

The benchmarks aren't keeping up with the runtime releases. Node 20 is already EOL and Node 22 is in maintenance state. Deno currently installed is also ancient -- current release is 2.8.3.

[hiSandog]

The runtime matrix should distinguish supported/LTS baselines from experimental current releases. Replacing Node 20/22 entirely loses useful historical and maintenance comparisons; a better default may be active LTS plus latest current, with older EOL data retained only in archived results. Pin exact Node/Deno patch versions and record runtime flags in each result so changes in V8 or permissions do not look like library regressions.