Refactors the CLI to create the `*codersdk.Client` in the handlers. This is groundwork for changing the `rootCmd.InitClient()` to use the new `ClientOption`s.
It also improves variable locality, scoping the Client to the handler. This makes misuse less likely and reduces the memory allocations to just the command being executed, rather than allocating a Client for every command regardless of whether it is executed.
Relates to https://github.com/coder/internal/issues/893
Instead of `coder task create <template> --input <input>`, it is now
`coder task create <input> --template <template>`.
If there is only one AI task template on the deployment, the
`--template` parameter can be omitted.
Cian Johnston