Allow referencing other env vars that include an exec block

[FalkWoldmann]

Hi, I would like to include env var that has an exec block in another env var, like

[env]
SERVICE_NAME = { value = "{{ exec(command='dasel -r toml -w plain -f Cargo.toml .package.name') }}", tools = true }
SOME_REF="/default/{{env.SERVICE_NAME}}"

But this does not work:

mise ERROR failed to parse template: '/default/{{env.SERVICE_NAME}}'
mise ERROR Failed to render '__tera_one_off'
mise ERROR Variable `env.SERVICE_NAME` not found in context while rendering '__tera_one_off'
mise ERROR Run with --verbose or MISE_VERBOSE=1 for more information

Setting some fixed value like SERVICE_NAME = "foo" works.