[SYCL][DOC] Add sycl_ext_oneapi_enqueue_functions (intel#11491)

Adds a new extension proposal to simplify enqueuing work to a device.

- Uses different function names for different use-cases.
- Uses free-functions instead of member functions.
- Requires developers to opt-in to the creation of event objects.

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Signed-off-by: John Pennycook <john.pennycook@intel.com>
Co-authored-by: Ben Ashbaugh <ben.ashbaugh@intel.com>
Co-authored-by: Greg Lueck <gregory.m.lueck@intel.com>