Address lint errors

[mjpieters]

• Remove unused config functions (these were moved to filter.go in 1bed38d)
• Use entries of mongodb bson.D result directly instead of using the deprecated Map method.
• Don't ignore err results from utility functions.

I really like being able to rely on make lint being clean, seeing errors there, even if not in my own PR changes, makes me itch. 😅

Specifically, these lint issues have been addressed:

golangci-lint run ./...
drivers/mysql/mysql.go:501:49: ineffectual assignment to err (ineffassign)
                strColumns, strParentTable, strParentColumns, err := parseFK(r.Def)
                                                              ^
drivers/mongodb/mongodb.go:98:27: SA1019: result.Map is deprecated: Converting directly from a D to an M will not be supported in Go Driver 2.0. Instead, users should marshal the D to BSON using bson.Marshal and unmarshal it to M using bson.Unmarshal. (staticcheck)
                for key, value := range result.Map() {
                                        ^
drivers/sqlite/sqlite.go:368:49: ineffectual assignment to err (ineffassign)
                strColumns, strParentTable, strParentColumns, err := parseFK(r.Def)
                                                              ^
config/config.go:553:6: func `excludeTableFromSchema` is unused (unused)
func excludeTableFromSchema(name string, s *schema.Schema) error {
     ^
config/config.go:908:6: func `matchLabels` is unused (unused)
func matchLabels(il []string, l schema.Labels) bool {
     ^

[mjpieters]

I suspect that these lint issues have been missed for some time because you set the golanglint action to use the github-pr-check reporter. These end up as error annotations on the workflow summary page (see my other PR workflow summary), and the lint check itself doesn't show an error.

I recommend you change the configuration for that action to make these more visible:

• You could enable fail_on_error to have the action fail the workflow when there are errors.
• You could try and see if the reporter: github-pr-review option is more visible.

[mjpieters]

Note: I chose this option over unmarshalling as a bson.M map to maintain the order preservation.

However by using result.Map() the order was already undone, and before this change the key-value pairs were iterated over in hash table order.

If this is now resulting in unexpected ordering changes, we could change the above to use var result bson.M instead and use for key, value := range result { for this loop.

[k1LoW]

@mjpieters Thank you!! I am very pleased with these improvements.