fix: ensure reproducibility of the ledger_suite_orchestrator_canister (stacked)

[basvandijk]

This is a cherry-pick of #5347 onto #5194.

The ledger_suite_orchestrator_canister is using a proc-macro from the aksama crate:

#[derive(Template)]
#[template(path = "dashboard.html")]
pub struct DashboardTemplate { ... }

This is known to cause non-determinism (askama-rs/askama#461) and it's causing the Build Reproducibility check to fail in: https://github.com/dfinity/ic/actions/runs/15296835171/job/43032042139?pr=5194. It's unclear why it didn't fail earlier.

We therefor apply the same work-around as in: rs/http_endpoints/public/build.rs and rs/ic_os/config/build.rs by loading the template in build.rs from a string instead of from a path.