Chore: update to use migrated functions from solvis/issues/37

[chrisbc]

When https://github.com/GNS-Science/solvis/issues/37 is closed and new solvis is released... then

• [x] update to new solvis release
• [x] convert local functions into wrappers for their solvis counterparts

[DrCuriosity]

Hi @chrisbc,

Have refactored to use the pre-release solvis-0.12.0-alpha.1 version of Solvis:

poetry run pip install git+https://github.com/GNS-Science/solvis@pre-release --no-deps

Commit: https://github.com/GNS-Science/solvis-graphql-api/commit/22b71b391ecf78e1616fd15f8036840f53e9ea34

Outstanding things:

• It's targeting the pre-release branch. Could we maybe do an official 0.12.0 release on the Solvis side to simplify things?
• Will need to redo the Poetry config, rather than pulling it in with pip
• I think I might need to do some dependency massaging work on solvis-store to ensure the updated nzshm-model version is compatible, too