RFR: 8294626: Improve URL protocol lower casing

[Claes Redestad]

On Fri, 30 Sep 2022 10:39:37 GMT, Claes Redestad <redestad at openjdk.org> wrote:

> Move a simple utility method from `URL` to the shared `sun.net.util.URLUtil` class, rename it for clarity and enhance it so that it returns the string literal if the protocol matches one of the tested variants. This helps reduce dependencies from bootstrap code on `Locale` while improving the performance and allocation pressure in certain applications.

`URLUtil` already exists, is used during bootstrap from non-java.net packages and would profit from reusing this lower case method. Making the method in `URL` public is a non-starter. I'd love having module-scoped visibility modifier (so we could share static utility methods without resorting to non-exported utility classes), but without that this was the best option to get the full benefit without duplicating the logic in places like `URLUtil.urlNoFragString`

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PR: https://git.openjdk.org/jdk/pull/10506