Avoid macro-expand recursion into `Expr(:toplevel, ...)` (#53515)
Here's an example output from macroexpand:
```
Expr
head: Symbol thunk
args: Array{Any}((1,))
1: Core.CodeInfo
code: Array{Any}((2,))
1: Expr
head: Symbol toplevel
args: Array{Any}((17,))
1: Expr
head: Symbol hygienic-scope
args: Array{Any}((3,))
1: LineNumberNode
2: Module Base.Enums
3: LineNumberNode
2: Expr
head: Symbol hygienic-scope
args: Array{Any}((3,))
1: Expr
2: Module Base.Enums
3: LineNumberNode
3: Expr
head: Symbol hygienic-scope
args: Array{Any}((3,))
1: LineNumberNode
2: Module Base.Enums
3: LineNumberNode
4: Expr
head: Symbol hygienic-scope
args: Array{Any}((3,))
1: Expr
2: Module Base.Enums
3: LineNumberNode
...
```
Currently fails during bootstrap with:
```
LoadError("sysimg.jl", 3, LoadError("Base.jl", 542, ErrorException("cannot document the following expression:\n\n#= mpfr.jl:65 =# @enum MPFRRoundingMode begin\n #= mpfr.jl:66 =#\n MPFRRoundNearest\n #= mpfr.jl:67 =#\n MPFRRoundToZero\n #= mpfr.jl:68 =#\n MPFRRoundUp\n #= mpfr.jl:69 =#\n MPFRRoundDown\n #= mpfr.jl:70 =#\n MPFRRoundFromZero\n #= mpfr.jl:71 =#\n MPFRRoundFaithful\n end\n\n'@enum' not documentable. See 'Base.@__doc__' docs for details.\n")))
```
Perhaps we can do better than wrapping each `Expr(:toplevel, ...)` arg
individually, or I should be filtering out the LineNumberNodes?
---------
Co-authored-by: Keno Fischer <keno@juliacomputing.com>
Co-authored-by: Keno Fischer <keno@juliahub.com>
