tvix/eval/value/function: check if BTreeMap or on-demand sorting is faster

#374
Opened by flokli at 2024-01-24T13·59+00

Spun out of https://cl.tvl.fyi/c/depot/+/10685/comments/86e2e9aa_1262e8f1.

We should benchmark if having the BTreeMap initially, or sorting on demand is faster in real-world scenarios.