RFR: 8323832: Load JVMCI with the platform class loader [v2]

[Alan Bateman]

On Tue, 23 Jan 2024 19:16:49 GMT, Doug Simon <dnsimon at openjdk.org> wrote:

>> This PR changes `jdk.internal.vm.ci` such that it is loaded by the platform class loader instead of the boot class loader. This allows Native Image to load a version of JVMCI different than the version on top of which Native Image is running. This capability is demonstrated and tested by `LoadAlternativeJVMCI.java`.
>
> Doug Simon has updated the pull request incrementally with one additional commit since the last revision:
> 
>   use null to denote boot class loader as delegation parent

test/hotspot/jtreg/compiler/jvmci/LoadAlternativeJVMCI.java line 50:

> 48:                 e = e + File.separator;
> 49:             }
> 50:             cp[i] = new URI("file:" + e).toURL();

This should be `cp[I] = file.toURI().toURL()` as a file path needs encoding to be URI path component.

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PR Review Comment: https://git.openjdk.org/jdk/pull/17520#discussion_r1464719091