Refactor errors to improve overall consistency

[joshuasing]

Summary
Refactor errors to help improve overall consistency.

Related: #27, #32

Changes

• Use errors.New instead of fmt.Errorf when formatting verbs are not used, preventing unnecessary parsing
• Use the %w verb in fmt.Errorf to wrap errors: https://pkg.go.dev/fmt#Errorf (%w verb)
• Make all errors begin with a lowercase letter: https://go.dev/wiki/CodeReviewComments#error-strings
• Remove "failed to" from start of errors, as this is often implied and makes errors longer and harder to read, e.g. failed to a: failed to b: failed to c: original error vs a: b: c: original error
• Use errors.Is for error comparison: https://pkg.go.dev/errors#Is
• Use errors.As for error conversion: https://pkg.go.dev/errors#As

[marcopeereboom]

OMGYES

[ClaytonNorthey92]

tests pass, I vote merge ✅