Standardize stdlib dependency knowledge location

[staticfloat]

We should have a single source of truth for stdlib dependency knowledge. As it stands, we have 2.5 separate places where this knowledge is encoded:

1. In stdlib Project.toml such as here
2. In pkgimage.mk, such as here.
   2.5. In sysimg.jl, such as here (Note, this one counts as 1/2 because only topological sort order is recorded, rather than a full dependency graph).

This makes it needlessly difficult to alter stdlib dependencies. Instead, we should automatically compute this from the Project.toml files in all cases. We should also record the sysimg/pkgimage decision in the same place, perhaps by setting a preference in the Project.toml?

[bkamins]

CC @nalimilan - the key points are:

• currently Statistics does not require entry in [compact] section so its version will be unspecified;
• what if in the future someone will want to use upgraded Statistics.jl version with an older version of Julia;

[vchuravy]

#51368 did part of this and after #51399 we have much fewer listed in sysimg.jl.

For the last step we do need a toml parser and then convert that to Makefiles variables. That seems obnoxious. Or we have something that autogenerated stdlib.mk for us...