use macro to make get_value methods more concise

[andygrove]

Following on from https://github.com/dask-contrib/dask-sql/pull/803, this PR demonstrates how we can use a macro to make some of the boilerplate code more concise.

More generally, this PR allows us to discuss whether we want to start using macros in this project.

Pro: Concise code

Con: Rust macros are another language to learn - https://doc.rust-lang.org/book/ch19-06-macros.html

[andygrove]

Macros could be useful for replacing other areas of boilerplate code such as implementing this for each operator:

impl TryFrom<LogicalPlan> for PyProjection {
    type Error = PyErr;

    fn try_from(logical_plan: LogicalPlan) -> Result<Self, Self::Error> {
        match logical_plan {
            LogicalPlan::Projection(projection) => Ok(PyProjection { projection }),
            _ => Err(py_type_err("unexpected plan")),
        }
    }
}

[codecov-commenter]

Codecov Report

Merging #821 (150643a) into main (34b7a4b) will decrease coverage by 0.17%. The diff coverage is n/a.

@@            Coverage Diff             @@
##             main     #821      +/-   ##
==========================================
- Coverage   77.38%   77.21%   -0.18%     
==========================================
  Files          75       75              
  Lines        4219     4217       -2     
  Branches      767      760       -7     
==========================================
- Hits         3265     3256       -9     
- Misses        784      786       +2     
- Partials      170      175       +5     

Impacted Files	Coverage Δ
dask_sql/physical/rex/core/literal.py	58.09% <0.00%> (-2.86%)	:arrow_down:
dask_sql/_version.py	32.76% <0.00%> (-1.13%)	:arrow_down:
dask_sql/physical/rel/custom/predict.py	91.66% <0.00%> (-0.23%)	:arrow_down:
dask_sql/utils.py	99.03% <0.00%> (-0.01%)	:arrow_down:

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