feat: Extend es to esm (#109)

Handle different cases to make format extension consistent across the plugins and different aliases.
Update integration tests to dynamically generate configs off a base so it's easier to handle a lot more cases.

GH #102

Author: nsdeschenes

.changeset/many-berries-grab.md

@@ -0,0 +1,8 @@
+---
+"@codecov/webpack-plugin": patch
+"@codecov/rollup-plugin": patch
+"@codecov/vite-plugin": patch
+"@codecov/bundler-plugin-core": patch
+---
+
+Modify output formats to be consistent across aliases and bundlers