## What changes were proposed in this pull request?
Add `ExecutorClassLoader.getResourceAsStream`, so that classes dynamically generated by the REPL can be accessed by user code as `InputStream`s for non-class-loading purposes, such as reading the class file for extracting method/constructor parameter names.
Caveat: The convention in Java's `ClassLoader` is that `ClassLoader.getResourceAsStream()` should be considered as a convenience method of `ClassLoader.getResource()`, where the latter provides a `URL` for the resource, and the former invokes `openStream()` on it to serve the resource as an `InputStream`. The former should also catch `IOException` from `openStream()` and convert it to `null`.
This PR breaks this convention by only overriding `ClassLoader.getResourceAsStream()` instead of also overriding `ClassLoader.getResource()`, so after this PR, it would be possible to get a non-null result from the former, but get a null result from the latter. This isn't ideal, but it's sufficient to cover the main use case and practically it shouldn't matter.
To implement the convention properly, we'd need to register a URL protocol handler with Java to allow it to properly handle the `spark://` protocol, etc, which sounds like an overkill for the intent of this PR.
Credit goes to zsxwing for the initial investigation and fix suggestion.
## How was this patch tested?
Added new test case in `ExecutorClassLoaderSuite` and `ReplSuite`.
Closes#23558 from rednaxelafx/executorclassloader-getresourceasstream.
Authored-by: Kris Mok <kris.mok@databricks.com>
Signed-off-by: gatorsmile <gatorsmile@gmail.com>
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