Middleware matching is too broad when using i18n

[serhalp]

There are a few scenarios where our the custom matchers from middleware are not correctly being transformed when using i18n and default locales, as they're either matching too broadly or too narrowly.

See also related #2472.

Data

The following is parsed automatically by the Next.js repo e2e test report generator.

test: Middleware custom matchers i18n should not match
reason: Middleware matching is too broad when using i18n