Allow any numeric value for BODY_SIZE_LIMIT in adapter-node

[Rich-Harris]

Describe the problem

From #11381 — it's unlikely but conceivable that someone would want to set a body size limit of zero. More to the point, it's arguably a bit weird that '0' actually means 'Infinity'.

It's also reasonable that someone would want to do something like BODY_SIZE_LIMIT=1e6 to express 'a megabyte'.

Describe the proposed solution

Allow any numeric JavaScript value, using parseFloat. Error if this results in NaN.

[codenoid]

ok let me take a look

[Rich-Harris]

closed via #11589