Add rule to remove unused variable

Coverage after merging remove-unused-identifiers into main will be

86.88%

Coverage Report for Changed Files

File	Stmts	Branches	Funcs	Lines	Uncovered Lines
src/nodes
block.rs	95.86%	100%	97.75%	95.50%	16, 19, 214–216, 25, 251–256, 26, 28, 31, 40, 49–50, 52, 55
src/nodes/statements
function.rs	92.36%	100%	88.73%	93.13%	128–130, 183–184, 186, 38, 388–389, 39, 390, 41, 410, 423, 446–447, 449
src/process
scope_visitor.rs	81.47%	100%	82.50%	81.30%	107–109, 112, 116, 140–142, 145, 149, 176–178, 190, 194, 242–252, 257, 281–283, 315–317, 63–65, 78–80, 83, 87
visitors.rs	99.08%	100%	100%	98.99%	92–97
src/process/processors
find_identifier.rs	96.30%	100%	100%	95.45%	68
find_usage.rs	100%	100%	100%	100%
src/rules
group_local.rs	89.29%	100%	78.95%	91.40%	38–40, 44
inject_value.rs	86.54%	100%	89.47%	86.04%	14, 150, 163, 165–177, 180–181, 187, 223–226, 229, 232, 74, 78–79, 87
mod.rs	89.25%	100%	77.78%	90.70%	112–114, 118, 128–130, 148–150, 152, 183–185, 278, 319–320, 355–357, 420–422, 73
no_local_function.rs	95.24%	100%	86.67%	97.10%
remove_call_match.rs	52.22%	100%	70%	50%	11, 125–130, 132, 134, 33–35, 56–57, 59–65, 67–76, 78–81, 86, 88, 96–98
remove_unused_variable.rs	94.86%	100%	92.59%	95.19%	119, 142–145, 147–148
src/rules/rename_variables
rename_processor.rs	98.86%	100%	97.92%	99.07%	10, 95
src/utils
expressions_as_statement.rs	24.14%	100%	25%	24.07%	14–26, 34, 40–51, 53–62, 64
mod.rs	97.18%	100%	97.56%	97.06%	56–57, 64

seaofvoices / darklua