Swap the hpagent dependency for https-proxy-agent

Replaces hpagent with https-proxy-agent in each package.json that declares it, in the same section and position, so the declaration order is left as it was. Where a source beneath the package.json still references hpagent — a usage the migration left in place, a mock, or a bundler configuration naming it — https-proxy-agent is added alongside and hpagent kept, since both are then needed. A package.json whose sources the migration didn't reach is left alone entirely, rather than gaining a dependency nothing uses. Lock files are not regenerated; run the package manager's install afterwards.