Replace usage of `Object.fromEntries` with `reduce`

[BPScott]

This PR contains a:

• [ ] bugfix
• [ ] new feature
• [x] code refactor
• [ ] test update
• [ ] typo fix
• [ ] metadata update

Motivation / Use-Case

Occasionally I need to test on legacy browsers. webpack-hot-middleware has pretty good support for older browsers but I've spotted a case where it could broaden its support. Replacing Object.fromEntries with reduce should bring back support for Chrome 49-72, Safari 10.1-12.0 and Firefox 44-62 (based upon comparing caniuse tables for Object.fromEntries and UrlSearchParams), assuming that "browsers that support UrlSearchParams" is the bottom boundary.

[linux-foundation-easycla[bot]]

The committers listed above are authorized under a signed CLA.

• :white_check_mark: login: BPScott / name: Ben Scott (b6be874d50eae4b6843899e6e269455cdac5b1a7)

[alexander-akait]

Thank you