[Relay][TOPI] Gluncv SSD support on the GPU (#2784)

[Relay][TOPI] Gluncv SSD support on the GPU (#2784)

* ssd gluoncv gpu op updated

* ssd gluoncv gpu op updated

* tutorials and testes modified

* tutorials and testes modified

* fix lint

* fix lint

* address comment

* multibox bug fixed

* space line added

* use less threads per block

* use less threads per block

* less threads per block for get valid count

* less threads per block for get valid count

* merge with master

* Revert "less threads per block for get valid count"

This reverts commit 08896cfccc34b0b2a1646d01d01ea4cad73941c4.

* Revert "less threads per block for get valid count"

This reverts commit 08896cfccc34b0b2a1646d01d01ea4cad73941c4.

* typo fixed

* elem length made to a variable

* fix lint error

* fix lint error

* lint fixed

* bug fixed

* bug fixed

* lint fixed

* error fixed

* error fixed

* test ci

* test ci

* seperate argsort to be an independent op

* seperate argsort to be an independent op

* fix lint

* fix lint

* remove unsupported models

* typo fixed

* argsort added to realy

* solve conflicts with master

* fix lint

* fix lint

* test push

* Revert "test push"

This reverts commit 6db00883fab6cc06bddf564c926bb27c874397d8.

* fix lint error

* fix more lint

* cpu test_sort udpated

* debug ci

* nms fixed

* expose argsort to relay frontend

* test ci

* fix lint

* sort register error fixed

* fix nnvm

* nms type fixed

* adaptive pooling added to relay

* Revert "adaptive pooling added to relay"

This reverts commit 1119f1f2c055753e0cc5611627597749134c5c8c.

* fix lint

* expose argsort op

* fix lint

* fix lint

* fix lint

* sort test updated

* sort bug fixed

* nnvm error fixed

* fix argsort default data type returned to be float insteaf of int

* fix lint

* fix lint

* test fixed

* fix valid count

* fix titanx bug

* tutorial add both targets

* titanx error fixed

* try to fix CI old gpu error

* try to solve CI GPU error

* get_valid_count added

* reverse get_valid_count

* get valid count optimized

* address comments

* fix ci error

* remove unessesary block sync

* add back one sync

* address comments

* address more comments

* more comments

* move sort to be indepent algorithm

* typo fixed

* more typos

* comments addressed

* doc updated

* fix pylint

* address final comments

* apache license added