By Iain Withers, Lawrence White and Huw Jones LONDON (Reuters) -After seven weeks in which Britain’s reputation for financial credibility has been rocked by political missteps, senior finance executives have given new prime minister Rishi Sunak a cautious welcome. Sunak is a known quantity to Britain’s banks, asset managers and insurers, having previously run the country’s finance ministry for two years as the COVID-19 pandemic took its toll on the economy. Finance bosses are hopeful his new administration will have a steadying influence on markets, after the deep tax-cutting plans of his pred…