LOWELL — Across the commonwealth, cities and towns are tightening their belts in anticipation of the end of COVID-19 emergency funding, decreased revenue streams, as well as pressure on existing budgets from rising costs. At the state level, Gov. Maura Healey put a freeze on hiring in parts of the executive branch through the end of the fiscal year in June. But in Lowell, in what could be a harbinger of what the 2025 budget process is going to l…