groot: streamline r/w buffer ops

[sbinet]

This CL streamlines a bit the r/w buffer operations:

• introduce {R,W}Buffer.{Read,Write}StdVector{T}
• rename all WriteFastArrayXXX into WriteArraXXX
• drop all error returns from {R,W}Buffer.{Read,Write}Object{,Any}
• use {Read,Write}Object intead of {Unm,M}arshalROOT
• properly handle std::vector<T=builtin> type generation

[codecov-commenter]

Codecov Report

Merging #901 (2a6495b) into main (1b25234) will increase coverage by 0.06%. The diff coverage is 58.11%.

@@            Coverage Diff             @@
##             main     #901      +/-   ##
==========================================
+ Coverage   73.80%   73.87%   +0.06%     
==========================================
  Files         399      400       +1     
  Lines       48336    48426      +90     
==========================================
+ Hits        35675    35775     +100     
- Misses      10293    10422     +129     
+ Partials     2368     2229     -139     

Impacted Files	Coverage Δ
groot/cmd/root-gen-type/main.go	19.69% <0.00%> (ø)
groot/rbytes/rbuffer_gen.go	54.16% <11.66%> (-30.36%)	:arrow_down:
groot/rphys/vector2.go	86.11% <28.57%> (-1.77%)	:arrow_down:
groot/rphys/vector3.go	88.63% <28.57%> (-1.61%)	:arrow_down:
groot/rtree/leaf.go	58.69% <33.33%> (-1.47%)	:arrow_down:
groot/rbase/objstring.go	79.31% <37.50%> (-9.16%)	:arrow_down:
groot/rphys/feldmancousins.go	89.13% <37.50%> (-1.57%)	:arrow_down:
groot/rdict/rdict.go	79.70% <40.17%> (-7.89%)	:arrow_down:
groot/rbytes/wbuffer.go	75.22% <42.85%> (-2.05%)	:arrow_down:
groot/rbytes/wbuffer_gen.go	47.84% <47.84%> (ø)
... and 34 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update 1b25234...2a6495b. Read the comment docs.