[refactor] Use PrimitiveType::type instead of DataType::type

[taichi-gardener]

Related issue = #1905

The goal of this PR is to remove usages of DataType.

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[codecov]

Codecov Report

Merging #1926 into master will increase coverage by 0.84%.
The diff coverage is 23.07%.

@@            Coverage Diff             @@
##           master    #1926      +/-   ##
==========================================
+ Coverage   42.91%   43.76%   +0.84%     
==========================================
  Files          45       45              
  Lines        6410     6202     -208     
  Branches     1101     1101              
==========================================
- Hits         2751     2714      -37     
+ Misses       3489     3319     -170     
+ Partials      170      169       -1     

Impacted Files	Coverage Δ
python/taichi/lang/util.py	32.93% <0.00%> (+0.38%)	⬆️
python/taichi/lang/kernel.py	71.39% <100.00%> (+0.35%)	⬆️
python/taichi/lang/__init__.py	40.45% <0.00%> (-2.17%)	⬇️
python/taichi/lang/ast_checker.py	70.58% <0.00%> (-1.64%)	⬇️
python/taichi/testing.py	75.00% <0.00%> (-0.72%)	⬇️
python/taichi/lang/linalg.py	89.33% <0.00%> (-0.67%)	⬇️
python/taichi/lang/meta.py	64.38% <0.00%> (-0.49%)	⬇️
python/taichi/misc/util.py	18.27% <0.00%> (-0.24%)	⬇️
python/taichi/misc/task.py	0.00% <0.00%> (ø)
python/taichi/tools/patterns.py	0.00% <0.00%> (ø)
... and 11 more

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[TH3CHARLie]

LGTM, just make sure to run ti format before the final merge