Issue 966 - Template jacobian_matrix and element_types with dimension.

[icui]

Description

• Template assembly::element_types with dimension.
• Template assembly::jacobian_matrix with dimension.
• Update boundary parameter to reference value.

Issue Number

Closes #965 and #966

Checklist

Please make sure to check developer documentation on specfem docs.

• I ran the code through pre-commit to check style
• THE DOCUMENTATION BUILDS WITHOUT WARNINGS/ERRORS
• I have added labels to the PR (see right hand side of the PR page)
• My code passes all the integration tests
• I have added sufficient unittests to test my changes
• I have added/updated documentation for the changes I am proposing
• I have updated CMakeLists to ensure my code builds
• My code builds across all platforms

[lsawade]

Already reviewed

[lsawade]

@Rohit-Kakodkar this good to go?