feat: integrate default detector into Enforcer

[Copilot]

fix: #1664

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[hsluoyz]

@copilot fix:

4 errors and 2 warnings
[golangci](https://github.com/casbin/casbin/actions/runs/20820439101/job/59807693186#step:4:29)
issues found
[golangci: enforcer_test.go#L733](https://github.com/casbin/casbin/pull/1665/files#annotation_43856678388)
File is not `goimports`-ed (goimports)
[golangci: enforcer.go#L195](https://github.com/casbin/casbin/pull/1665/files#annotation_43856678401)
File is not `goimports`-ed (goimports)
[golangci: detector/default_detector.go#L73](https://github.com/casbin/casbin/pull/1665/files#annotation_43856678419)
File is not `goimports`-ed (goimports)

[Copilot]

@copilot fix:

...

Fixed in commit 0a2cfe8. Ran goimports on all three files to remove trailing whitespace from blank lines.