Make Base.donotdelete public

[LilithHafner]

I rely on Base.donotdelete in Chairmarks.jl and I'd like it to be public. I imagine that other benchmarking tools also rely on it. It's been around since 1.8 (see also: #55773) and I think we should commit to keeping it functional for the rest of 1.x.

[nsajko]

donotdelete is actually defined in Core, and it's a built-in, as opposed to a generic function. As far as I understand exposing non-generic functions isn't a good practice. Perhaps it'd make sense to define something like this in Base, and make that public:

function donotdelete(args...)
    Core.donotdelete(args)
end