LAMA to Dask: replace `func` usage with Dask built-ins

[sadielbartholomew]

To do the follow-up work summarised under the heading 'Context and plan/proposal for follow-on work' in #300 (comment), i.e:

... such methods are more efficiently daskified by conversion to using the existing Dask built-in equivalents instead of calling func this way.

So the plan is to use follow-on PRs to convert from use of func to the appropriate built-in in each method. It turns out there are Dask built-ins for every one listed above available for us to use directly.

Methods to convert

• the eight trigonometric and hyperbolic methods and their inverses which don't have restricted domains (all except arccos, arcsin, arctanh and arccosh);
• ceil;
• exp;
• floor;
• rint;
• round;
• trunc;
• log.

[sadielbartholomew]

Closed by #308 and #309.