Supporting OpenCL 1.1

Overall the CTS usually assumes that at least OpenCL 1.2 is being used/tested. The main changes are to add missing `Version(1, 2)` to tests validating 1.2 features, and using/enabling corresponding extensions prior to them having been merged into core (like cl_khr_fp64, for example).

(Initial list of) tests to update:
* [ ] api
* [ ] Allow OpenCL 1.1 devices (api_min_max,queries);
* [ ] Add `Version(1, 2)`.
* [ ] basic
* [ ] Enable cl_khr_fp64.
* [ ] buffers
* [ ] Add `Version(1, 2)`.
* [ ] device_partition
* [ ] Add `Version(1, 2)`.
* [ ] events
* [ ] Add `Version(1, 2)`.
* [ ] images
* [ ] Add `Version(1, 2)`.
* [ ] mem_host_flags
* [ ] Add `Version(1, 2)`.

Start with the listed CTS areas: api, basic, buffers, device_partition, events, images, and mem_host_flags. Compare their existing version checks and extension handling, then update the OpenCL 1.2 assumptions so OpenCL 1.1 devices are supported where specified. Done means the checklist is covered and the affected conformance tests pass for OpenCL 1.1.

Written by the indexing model from the issue text.