[llvm] [Offload] Add an `unloadBinary` interface to PluginInterface (PR #143873)

[Joseph Huber via llvm-commits]

================
@@ -13,7 +13,9 @@
 def : Function {
     let name = "olCreateProgram";
     let desc = "Create a program for the device from the binary image pointed to by `ProgData`.";
-    let details = [];
+    let details = [
+        "`ProgData` must remain valid for the entire lifetime of the output `Program` handle",
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jhuber6 wrote:

Yes, the idea is that the returned program handle owns the associated memory. If the user doesn't want it anymore they unload it. That's how the other APIs do it because it's really bad to have your program crash because a user deallocated some random pointer ten days later.

https://github.com/llvm/llvm-project/pull/143873