For GPUCompiler we would like to support a native on disk cache of LLVM IR.
One of the longstanding issues has been the cache invalidation of such an on disk cache.

With #52233 we now have an integrated cache for the inference results and we can rely
on CodeInstance to be stable across sessions. Due to #52119 we can also rely on the
objectid to be stable.

My inital thought was to key the native disk cache in GPUCompiler on the objectid of
the corresponding CodeInstance (+ some compilation parameters).

While discussing this with @rayegun yesterday we noted that having a CodeInstance with
the same objectid might not be enough provenance. E.g we are not gurantueed that the
CodeInstance is from the same build artifact and the same precise source code.

For the package images we are tracking this during loading and validate all contents
at once, and we keep explicitly track of the provenance chain.

This PR adds a lookup up table where we map from "external_blobs" e.g. loaded images,
to the corresponding top module of each image, and uses this to determine the
build_id of the package image.

Objects that are not perma allocated are mapped to Main.
Main itself is a bit weird:

julia> @ccall jl_object_in_image(Main::Any)::UInt8
0x01

julia> Base.object_build_id(Main)
0xfdfcfbfa451e371b0000195de4fe8b4b

julia> Base.module_build_id(Main)
0xfdfcfbfa451e371b000018c746ebb6a2

julia> Base.module_build_id(Base)
0xfdfcfbfa451e371b0000195de4fe8b4b

julia> Base.object_build_id(Base)
0xfdfcfbfa451e371b0000195de4fe8b4b

julia> Base.Main == Main
true

So Main is itself perma-allocated through Base and thus the sysimage.

julia> @ccall jl_istopmod(Main::Module)::UInt8
0x00

julia> @ccall jl_istopmod(Base::Module)::UInt8
0x01

Main itself is not a topmod. So maybe it is not correct module to return for
runtime allocated objects.

Edit: I changed this to return nothing for runtime allocated objects.