Fixing trivial clippy warnings

[alienscience]

• Partial ne is automatically created
• Collapse else { if ... to else if
• Use ok_or_else() instead of ok_or() when calling functions
• Use .sum() instead of .fold(0, |a, b| a + b)
• Remove unneeded .into()
• Drop key name in struct literals where all key names === value names
• Use .is_empty() instead of .len() == 0