[Feature] : Add grid_sampler TensorRT Plugin

[grimoire]

This PR add grid_sampler TensorRT plugin.
Please register symbolics before converting onnx.

from mmcv.onnx.symbolic import register_extra_symbolics
register_extra_symbolics(11)

[codecov]

Codecov Report

Merging #865 (64cb2b3) into master (9ba1f76) will decrease coverage by 1.72%.
The diff coverage is 75.00%.

@@            Coverage Diff             @@
##           master     #865      +/-   ##
==========================================
- Coverage   66.59%   64.86%   -1.73%     
==========================================
  Files         145      148       +3     
  Lines        8818     9193     +375     
  Branches     1602     1647      +45     
==========================================
+ Hits         5872     5963      +91     
- Misses       2630     2903     +273     
- Partials      316      327      +11     

Flag	Coverage Δ
unittests	64.86% <75.00%> (-1.73%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
mmcv/onnx/symbolic.py	40.60% <75.00%> (+0.71%)	⬆️
mmcv/cnn/utils/weight_init.py	91.57% <0.00%> (-7.24%)	⬇️
mmcv/runner/base_module.py	79.41% <0.00%> (-6.31%)	⬇️
mmcv/image/io.py	88.37% <0.00%> (-2.39%)	⬇️
mmcv/image/photometric.py	99.26% <0.00%> (-0.74%)	⬇️
mmcv/image/geometric.py	94.19% <0.00%> (-0.28%)	⬇️
mmcv/ops/__init__.py	100.00% <0.00%> (ø)
mmcv/image/__init__.py	100.00% <0.00%> (ø)
mmcv/cnn/bricks/registry.py	100.00% <0.00%> (ø)
mmcv/cnn/bricks/conv_module.py	100.00% <0.00%> (ø)
... and 4 more

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[Johnson-Wang]

Hi, thanks for your contribution. I wonder if it is okay to create a relevant PR in mmdetection for mask-rcnn conversion.

[grimoire]

@Johnson-Wang Sure! That would be cool!

[Johnson-Wang]

The fp16 implement is not emergent for now. Therefore, this PR is thought ready to merge.