[SYCL] Deprecate access::mode (#22803)
`access::mode` is deprecated in SYCL 2020 in favor of `access_mode`.
Some enum entries are also deprecated - `discard_write`,
`discard_read_write` and `atomic`.
`access::mode` should be defined as:
```
using mode = sycl::access_mode;
```
Align the implementation with SYCL 2020 under
`__INTEL_PREVIEW_BREAKING_CHANGES`.
Update E2E tests to use `no_init` property for discard write.
