Tag kernel binaries with target and transformation stage and check if binary is appropriate when loading

[alexmarkov]

Kernel binaries are very flexible and serve many different purposes: they can be used by different back-ends, certain tools and consumed by the front-end. However, kernel files are not universal: kernel binary generated for one back-end cannot be used by another; kernel binary after whole-program transformations can only be consumed by AOT compiler and cannot be used by the front-end etc.

It would be nice to add certain information about target/stage/purpose of the kernel binary into the Component header. The following would be useful:

• name of the target (back-end);
• whether kernel can be consumed by the front-end;
• whether it is full (contains core libraries) or partial;
• whether it was transformed with whole-program transformations.

After adding that information we can add user-friendly error messages when user attempts to use incorrect kernel binary, for example when feeding AOT kernel binary back to the front-end (happened recently).

@johnniwinther @jensjoha WDYT?

/cc @sigmundch

[alexmarkov]

Found related old issue: #31545.
We should probably also record if --track-widget-creation was used when generating kernel (as this option also makes kernel incompatible).

[johnniwinther]

I think we should do this.