[MC-124365] Exiting world does not release file handle to zipped datapack / resourcepack

open Minecraft
open a world that contains a zipped datapack in its datapacks directory
after world is loaded, save & exit back to title screen
in windows file explorer, navigate to datapacks directory and try to delete the .zip file of the datapack

EXPECTED:
file can be deleted

ACTUAL:
file cannot be deleted because it is still in use by java process (Minecraft sitting at title screen)

NOTES:
you can work around it by closing Minecraft, or by opening a different world (at which point MC seems to 'flush' its datapacks)

Ideally, Minecraft should only be using the file during load/reload - once loading is complete, it should release the file handle. (for non-zip files, like functions in a datapack, you can delete each while the world is loaded)

Error 20w17a

Failed to delete world World
java.nio.file.FileSystemException: ###\saves\World\datapacks\my-datapack.zip: The process cannot access the file because it is being used by another process.

	at sun.nio.fs.WindowsException.translateToIOException(WindowsException.java:86)
	at sun.nio.fs.WindowsException.rethrowAsIOException(WindowsException.java:97)
	at sun.nio.fs.WindowsException.rethrowAsIOException(WindowsException.java:102)
	at sun.nio.fs.WindowsFileSystemProvider.implDelete(WindowsFileSystemProvider.java:269)
	at sun.nio.fs.AbstractFileSystemProvider.delete(AbstractFileSystemProvider.java:103)
	at java.nio.file.Files.delete(Files.java:1126)
	at czj$a$1.a(SourceFile:285)
	at czj$a$1.visitFile(SourceFile:280)
	at java.nio.file.Files.walkFileTree(Files.java:2670)
	at java.nio.file.Files.walkFileTree(Files.java:2742)
	at czj$a.f(SourceFile:280)
	at dsw$a.a(SourceFile:334)
	at dsw$a$$Lambda$4354/456574378.accept(Unknown Source)
	at dok.b(SourceFile:43)
	at dok$$Lambda$4355/1901085596.onPress(Unknown Source)
	at dmc.as_(SourceFile:20)
	at dlw.a(SourceFile:16)
	at dma.a(SourceFile:150)
	at dmz.a(SourceFile:27)
	at dks.b(SourceFile:86)
	at dks$$Lambda$2375/1247247257.run(Unknown Source)
	at dpj.a(SourceFile:416)
	at dks.a(SourceFile:86)
	at dks.c(SourceFile:150)
	at dks$$Lambda$2374/599726537.run(Unknown Source)
	at alp.execute(SourceFile:94)
	at dks.b(SourceFile:150)
	at dks$$Lambda$1747/1735688275.invoke(Unknown Source)
	at org.lwjgl.glfw.GLFWMouseButtonCallbackI.callback(GLFWMouseButtonCallbackI.java:36)
	at org.lwjgl.system.JNI.invokeV(Native Method)
	at org.lwjgl.glfw.GLFW.glfwPollEvents(GLFW.java:3101)
	at com.mojang.blaze3d.systems.RenderSystem.flipFrame(SourceFile:105)
	at dft.e(SourceFile:301)
	at dkr.e(SourceFile:1027)
	at dkr.d(SourceFile:630)
	at net.minecraft.client.main.Main.main(SourceFile:204)