refactor(misc): replace fmt.Errorf with errors.New where possible

[jvoisin]

No need to to invoke the whole Printf machinery for constant strings. While this shouldn't have an impact on memory consumption nor allocation (as constructing errors to return is never in a hot path), this should reduce a bit the code size, as errors.New will be inlined to a simple struct initialization instead of a function call.

[fguillot]

Let's fix all of them while you are at it. After that, we can have a linter check.

go install github.com/catenacyber/perfsprint@latest
perfsprint ./...

Remaining things to fix which can be fixed automatically with perfsprint -fix ./...

/home/fred/repos/miniflux/v2/internal/integration/linkwarden/linkwarden.go:30:10: error-format: fmt.Errorf can be replaced with errors.New
/home/fred/repos/miniflux/v2/internal/integration/linkwarden/linkwarden.go:9:2: fiximports: Fix imports
/home/fred/repos/miniflux/v2/internal/googlereader/handler.go:282:9: error-format: fmt.Errorf can be replaced with errors.New
/home/fred/repos/miniflux/v2/internal/googlereader/handler.go:1016:39: integer-format: fmt.Sprint can be replaced with faster strconv.FormatInt
/home/fred/repos/miniflux/v2/internal/googlereader/handler.go:1016:100: integer-format: fmt.Sprint can be replaced with faster strconv.FormatInt
/home/fred/repos/miniflux/v2/internal/googlereader/handler.go:1050:26: error-format: fmt.Errorf can be replaced with errors.New
/home/fred/repos/miniflux/v2/internal/googlereader/item.go:61:15: error-format: fmt.Errorf can be replaced with errors.New
/home/fred/repos/miniflux/v2/internal/googlereader/request_modifier.go:52:28: string-format: fmt.Sprintf can be replaced with string concatenation
/home/fred/repos/miniflux/v2/internal/googlereader/request_modifier.go:53:28: string-format: fmt.Sprintf can be replaced with string concatenation
/home/fred/repos/miniflux/v2/internal/googlereader/item.go:7:2: fiximports: Fix imports
/home/fred/repos/miniflux/v2/client/client.go:128:29: string-format: fmt.Sprintf can be replaced with string concatenation

[jvoisin]

I was in the process of writing a linter :P