Adjust ToStringKey use unpack params, fix pass []any as any in variadic function

[alingse]

• Do only one thing
• Non breaking API changes
• Tested

What did this pull request do?

i am writing a linter to lint my silly bug in work.
and run github Actions for some top go packages, gorm failed here

Error: /home/runner/work/asasalint/asasalint/gorm/callbacks/associations.go:209:38: pass []any as any to func ToStringKey func(values ...interface{}) string
Error: /home/runner/work/asasalint/asasalint/gorm/callbacks/associations.go:29[5](https://github.com/alingse/asasalint/runs/7263106786?check_suite_focus=true#step:7:6):38: pass []any as any to func ToStringKey func(values ...interface{}) string
Error: /home/runner/work/asasalint/asasalint/gorm/migrator/migrator.go:201:29: pass []any as any to func append func([]interface{}, ...interface{}) []interface{}

these three is not bug (migrator/migrator.go:201 is by desgin)

ToStringKey's current usage worked, but change to use unpacked params might be better.

User Case Description