StatementList: Rename statements to items

[AnnikaCodes]

This Pull Request fixes/closes #842

It changes the following:

• Renames the statements property of the StatementList struct to items
• Renames the StatementList::statements() function to StatementList::items()

[codecov]

Codecov Report

Merging #1014 (26a4762) into master (a068ef2) will decrease coverage by 0.04%.
The diff coverage is 80.00%.

@@            Coverage Diff             @@
##           master    #1014      +/-   ##
==========================================
- Coverage   59.83%   59.79%   -0.05%     
==========================================
  Files         167      167              
  Lines       11018    11087      +69     
==========================================
+ Hits         6593     6629      +36     
- Misses       4425     4458      +33     

Impacted Files	Coverage Δ
...ax/ast/node/declaration/async_function_decl/mod.rs	22.22% <0.00%> (ø)
...ax/ast/node/declaration/async_function_expr/mod.rs	24.00% <0.00%> (ø)
boa/src/syntax/ast/node/statement_list/mod.rs	48.71% <83.33%> (ø)
boa/src/syntax/ast/node/block/mod.rs	56.66% <100.00%> (ø)
...ax/ast/node/declaration/arrow_function_decl/mod.rs	60.86% <100.00%> (ø)
...c/syntax/ast/node/declaration/function_decl/mod.rs	68.42% <100.00%> (ø)
...c/syntax/ast/node/declaration/function_expr/mod.rs	61.29% <100.00%> (ø)
boa/src/syntax/ast/node/switch/mod.rs	61.42% <100.00%> (ø)
boa/src/syntax/parser/expression/assignment/mod.rs	50.58% <0.00%> (-12.95%)	⬇️
boa/src/syntax/parser/expression/mod.rs	81.89% <0.00%> (-10.65%)	⬇️
... and 11 more

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[AnnikaCodes]

The Clippy failures are unrelated to this change; #1015 addresses them.