Fix new lints for Rust 1.73

[jedel1043]

This also removes the clippy::nursery lint level because it's filled with experimental lints that most of the time show warnings on false-positives.

[github-actions]

Test262 conformance changes

Test result	main count	PR count	difference
Total	95,574	95,574	0
Passed	75,273	75,273	0
Ignored	19,482	19,482	0
Failed	819	819	0
Panics	0	0	0
Conformance	78.76%	78.76%	0.00%

[codecov]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (8ae39af) 49.55% compared to head (59ceddd) 49.55%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3361      +/-   ##
==========================================
- Coverage   49.55%   49.55%   -0.01%     
==========================================
  Files         446      446              
  Lines       43712    43705       -7     
==========================================
- Hits        21663    21656       -7     
  Misses      22049    22049              

Files	Coverage Δ
boa_ast/src/lib.rs	75.00% <ø> (ø)
boa_cli/src/main.rs	0.60% <ø> (ø)
boa_engine/src/builtins/string/mod.rs	57.49% <100.00%> (ø)
boa_engine/src/bytecompiler/mod.rs	67.09% <ø> (-0.09%)	⬇️
boa_engine/src/lib.rs	73.33% <ø> (ø)
boa_engine/src/string/mod.rs	65.89% <100.00%> (ø)
boa_engine/src/value/conversions/mod.rs	67.24% <ø> (ø)
boa_engine/src/value/operations.rs	49.69% <100.00%> (ø)
boa_gc/src/lib.rs	99.45% <100.00%> (ø)
boa_icu_provider/src/lib.rs	100.00% <ø> (ø)
... and 9 more

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