[RNTuple] write multiple fields

[Moelf]

Nitems = 10
       data = [5, 6, 7, 8, 9, 10, 11, 12, 13, 14]
       newtable = Dict(
               "x1" => Float64.(data),
               "x2" => Float32.(data),
               "x3" => Int32.(data),
               "y1" => UInt16.(data),
           )
       UnROOT.write_rntuple(open("/tmp/a.root", "w"), newtable; rntuple_name="myntuple")
       LazyTree("/tmp/a.root", "myntuple")
 Row │ x1       y1      x2       x3
     │ Float64  UInt16  Float32  Int32
─────┼─────────────────────────────────
 1   │ 5.0      5       5.0      5
 2   │ 6.0      6       6.0      6
 3   │ 7.0      7       7.0      7
 4   │ 8.0      8       8.0      8
 5   │ 9.0      9       9.0      9
 6   │ 10.0     10      10.0     10
 7   │ 11.0     11      11.0     11
 8   │ 12.0     12      12.0     12
 9   │ 13.0     13      13.0     13
 10  │ 14.0     14      14.0     14

ROOT is now happy

$ root --version
ROOT Version: 6.33.01
Built for linuxx8664gcc on Oct 03 2024, 22:53:26
From heads/master@v6-31-01-3492-g65de35a80f

$ python
Python 3.11.9 (main, Jun 24 2024, 14:32:54) [GCC 11.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import ROOT
df  =  ROOT.RDataFrame("myntuple", "/tmp/a.root")
[ROOT.NTuple] Warning /build/jenkins/workspace/lcg_nightly_pipeline/build/projects/ROOT-HEAD/src/ROOT/HEAD/tree/ntuple/v7/src/RPageStorageFile.cxx:326 in ROOT::Experimental::Internal::RPageSourceFile::LoadStructureImpl()::<lambda()>:0: RuntimeWarning: Pre-release format version: RC 2
>>> df.GetColumnNames()
vector<string>{ "x1", "x2", "x3", "y1" }
>>> list(df.Take['std::int32_t']("x3"))
[5, 6, 7, 8, 9, 10, 11, 12, 13, 14]
>>> list(df.Take['float']("x2"))
[5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 11.0, 12.0, 13.0, 14.0]

• Do round trips within UnROOT.jl
• make ROOT happy

[codecov]

Codecov Report

Attention: Patch coverage is 89.02439% with 9 lines in your changes missing coverage. Please review.

Project coverage is 84.65%. Comparing base (10599f9) to head (1094f62).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/RNTuple/Writing/page_writing.jl	82.05%	7 Missing ⚠️
src/RNTuple/Writing/TFileWriter.jl	97.56%	1 Missing ⚠️
src/RNTuple/footer.jl	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #349      +/-   ##
==========================================
+ Coverage   84.57%   84.65%   +0.07%     
==========================================
  Files          21       21              
  Lines        2976     3043      +67     
==========================================
+ Hits         2517     2576      +59     
- Misses        459      467       +8     

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[Moelf]

the current "C++ ROOT read back" CI setup is a bit janky, it will be better once there exists a ROOT release with 1.0.0 RNTuple spec.

I also would want to move to using Julia's Artifacts system for distribution test .root files, but for now maybe this is good enough.

Another thing is I bumped version of Julia and StaticArrays, @tamasgal can you let me know if you guys all moved to at least 1.10?

[tamasgal]

Yes that's fine, keep moving!