Expose write access to workers' scripts "create tail" endpoint as a separate token permission

https://github.com/cloudflare/cloudflare-rs/blob/bb294900b8a46ba69cf2aa23dd5c449ef45d01d3/cloudflare/src/endpoints/workers/create_tail.rs#L6

Originally filed as cloudflare/wrangler#1563 which has more context.

It would be nice to grant permission to "read" logs from workers independently of granting permission to write arbitrary workers scripts. It would be great if this could be brought in under account permission `1a71c399035b4950a1bd1466bbe4f420`: *Workers Scripts Read*.