[drone] import should translate invalid characters in secret IDs

[jimsheldon]

Similar to what we did in drone/go-convert#108, the import command for Drone should translate invalid characters to safe characters allowed in Harness secret IDs.

For example, MY-SECRET is valid in Drone, but it is an invalid Harness secret ID. In the Harness API call, MY-SECRET should convert to MY_SECRET (the name of the secret can remain MY-SECRET).

[jimsheldon]

It seems this work is still required.

The secret name and ID are created from just the secret name, which can have invalid characters since it comes directly from the export.

https://github.com/harness/harness-migrate/blob/master/internal/migrate/import.go#L101C23-L101C23
https://github.com/harness/harness-migrate/blob/master/internal/util/util.go#L32-L33