[ATen-vulkan][EZ] Bug fixes: only create the image view when memory has been bound, invalidate cmd on flush (#121027)
Summary:
## Context
Introduce some simple bug fixes to the Vulkan Compute API that were causing errors on Android.
1. When using deferred allocation for image textures, it is undefined behaviour to create a `vkImageView` for a `vkImage` that has not yet been bound to memory. Fix this by creating the image view only after the `vkImage` has been bound to memory.
2. When flushing the `api::Context`, the command pool is flushed but any current command buffers are not invalidated. This will cause a segmentation fault if the command buffer is not submitted prior to calling `flush()`, because subsequent calls to `submit_*_job()` will use the old command buffer which will have been freed when the command pool is flushed. To fix, invalidate any existing command buffers when calling `flush()`.
Test Plan:
Build the test binary for Android:
```
buck build --target-platforms=ovr_config//platform/android:arm64-fbsource -c ndk.custom_libcxx=false //xplat/caffe2:pt_vulkan_api_test_bin --show-output
```
Push and run the test binary on a local android phone.
Differential Revision: D54425370
Pull Request resolved: https://github.com/pytorch/pytorch/pull/121027
Approved by: https://github.com/mcr229, https://github.com/cbilgin
