This PR reduces ClimaCore memory usage due to excessive code inlining, and it closes #1064.

Specifically, it

• Removes the @inline annotations to Base.copyto! that were added in Inline copyto! to fix Ref allocations #945 and Extend and fix Ref broadcasting with StencilCoefs #978.
• Removes all slurm_mem increases from the CI pipeline, so that the default value of 8GB applies to every task.
• Extends broadcasting over Fields and DataLayouts so that it can handle single-element Tuples. In theory, broadcasting with a single-element Tuple should be equivalent to broadcasting with a Ref. However, since a Ref is mutable, it looks like the compiler needs to perform runtime allocations when using a Ref, unless we force it to inline the majority of the broadcasting machinery.
• Replaces every Ref in test/Fields/field_opt.jl with a single-element Tuple, so that the runtime allocation unit tests can pass.
• Replaces two of the @test_brokens in test/Operators/finitedifference/opt_examples.jl with @tests, since those tests are now passing, even though they don't appear to have anything to do with Refs.

Note: It is still necessary to go through the rest of our code (both in ClimaCore and elsewhere) and replace every Ref in a Field/DataLayout broadcast with a single-element Tuple. Now that the @inline annotations have been removed, broadcasting with a Ref will trigger runtime allocations, which will pose a problem for our long runs.

• Code follows the style guidelines OR N/A.
• Unit tests are included OR N/A.
• Code is exercised in an integration test OR N/A.
• Documentation has been added/updated OR N/A.