* add FLAGS_enable_api_kernel_fallback

* deal with more cases

* add ut for coverage

* [CustomDevice] add process_group_xccl ut

* update

* [CustomDevice] register Copy for custom device

* [CustomDevice] register Copy for custom device

* [CustomDevice] register Copy for custom device

* merge and add uts

* merge and add uts

* fix for blocking and unittests coverage

* [Plugin] Fix Custom device in eager mode, test=develop

* update test case, test=develop

* update ut for coverage, test=develop

* [CustomKernel] add capi eager mode support

* add ut

* add capi test

* Dataloader add custom device support

* update test=document_fix