What would you like to be added:
Introduce new ProviderSpecific options for the Route53 provider, such as:

aws/alias-disable-aaaa: "true" (disable AAAA Alias creation, only create A Alias record)
aws/alias-disable-a: "true" (disable AAAA Alias creation, only create AAAA Alias record)

By default, external-dns creates both A and AAAA Alias records. With these options, users could selectively disable either record type on a per-record basis.
Why is this needed:

Currently, the only way to prevent AAAA records is --exclude-record-types=AAAA, which disables them globally.

In real-world scenarios, users may want finer control:

• IPv4-only backends (disable AAAA for specific records)
• IPv6-only services (disable A for specific records)
• Phased migrations where only one protocol family should be exposed

A ProviderSpecific option avoids the need for manual DNS adjustments and keeps external-dns as the single source of truth.

If maintainers agree with this direction, I would be happy to work on a PR to implement it.