Support for intergrid kernels with stencil access

The PSyKAl-lite function `invoke_prolong_scalar_linear_kernel_type` exists in LFRic apps `science/gungho/source/psy/psykal_lite_mod`, and is called by `science/gungho/source/algorithm/core_dynamics/intermesh_mappings_alg_mod.x90`.

This PSyKAl-lite function was initially needed because PSyclone didn't support intergrid kernels with stencil access (see [PSyclone #1983](https://github.com/stfc/PSyclone/issues/1983)). This issue seems to now be closed and potentially resolved so the PSyKAl-lite code might be able to be removed.

Start by reading the PSyKAl-lite function in science/gungho/source/psy/psykal_lite_mod and its call in science/gungho/source/algorithm/core_dynamics/intermesh_mappings_alg_mod.x90. Check PSyclone #1983 to confirm whether intergrid kernels with stencil access are supported now. Done means confirming whether the workaround can be removed and identifying all affected references.

Written by the indexing model from the issue text.