feat: prevent log allocation unless needed

[nilslice]

Is blocked by:

• Rust SDK: feat(runtime): add log level set/get for pdk control extism#758
• Go SDK: feat!: provide plugins get_log_level runtime function & support levels go-sdk#74
• JS SDK: feat: make get_log_level available to plugin, respect log level js-sdk#85

TODO:

• add "off" case e.g.

if level == tracing::level_filters::LevelFilter::OFF {
        output[0] = Val::I32(i32::MAX)
...

Expect CI to fail as this PR includes new (unreleased) runtime functions

[nilslice]

("off" case is already handled via max int32 being impossible to exceed by user-set log level)

[zshipko]

Oops, I forgot there was already a PR for this. Closing because it's done in #48