[REVIEW] Fix concurrent JSON reads crash

[vuule]

Closes: #5934

Root cause:
A temporary unique_ptr to a mutable_table_device_view object was being passed to device_scalar. The error only reproes if a concurrent thread/process changes the content at the temporary location - no repro with a singlethreaded read.

Fix:
This PR contains a simple fix, and a few fixes for incorrect stream use in the JSON reader.

[GPUtester]

Please update the changelog in order to start CI tests.

View the gpuCI docs here.

[jrhemstad]

I'll approve since this is a release blocker and I know cuIO code is going to undergo a refactor in the near future, but passing a view type by pointer is smelly.

[vuule]

I'll approve since this is a release blocker and I know cuIO code is going to undergo a refactor in the near future, but passing a view type by pointer is smelly.

Changed the parameter to thrust::optional.

[codecov]

Codecov Report

Merging #6003 into branch-0.15 will decrease coverage by 4.10%.
The diff coverage is n/a.

@@               Coverage Diff               @@
##           branch-0.15    #6003      +/-   ##
===============================================
- Coverage        88.65%   84.54%   -4.11%     
===============================================
  Files               57       81      +24     
  Lines            10945    13845    +2900     
===============================================
+ Hits              9703    11705    +2002     
- Misses            1242     2140     +898     

Impacted Files	Coverage Δ
python/cudf/cudf/core/dtypes.py	88.39% <0.00%> (-8.54%)	⬇️
python/cudf/cudf/core/abc.py	91.48% <0.00%> (-2.96%)	⬇️
python/cudf/cudf/core/frame.py	89.76% <0.00%> (-1.42%)	⬇️
python/cudf/cudf/utils/ioutils.py	86.13% <0.00%> (-1.21%)	⬇️
python/dask_cudf/dask_cudf/sorting.py	93.12% <0.00%> (-0.99%)	⬇️
python/cudf/cudf/core/indexing.py	95.22% <0.00%> (-0.68%)	⬇️
python/cudf/cudf/utils/dtypes.py	85.79% <0.00%> (-0.64%)	⬇️
python/cudf/cudf/core/column/column.py	87.04% <0.00%> (-0.33%)	⬇️
python/cudf/cudf/core/column/numerical.py	94.25% <0.00%> (-0.13%)	⬇️
python/cudf/cudf/core/column/categorical.py	93.61% <0.00%> (-0.10%)	⬇️
... and 61 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 3d1f862...2c22d23. Read the comment docs.

[vuule]

rerun tests

[galipremsagar]

rerun tests

[kkraus14]

rerun tests