Added caching for Helm charts in deploy workflow

[roberto-mondello-dgt]

This PR integrates actions/cache@v3 into deploy pipeline to cache and restore the ./charts directory. Caching is keyed on the hash of Chart.yaml, so the cache is automatically invalidated whenever the chart definition changes.
In general:

• Avoid re-downloading charts on every run, speeding up deploy times.
• On a cache hit, the pipeline restores a previously built chart set; on a miss, the cache is regenerated automatically.
• Applied identically to both the “microservice” (deploy_ms) and “cronjob” (deploy_cj) deploy jobs.