RFR 8242260: Remove customizable ContentSigner from jarsigner

[Sean Mullan]

On 4/11/20 11:04 AM, Weijun Wang wrote:
> 2. Keep the options and update the deprecated classes to work with new signature algorithms. The update will likely to be 2 new methods and deprecating one existing.

Not sure if I understand this option, but I assume this is about adding 
RSASSA-PSS support to jarsigner. Perhaps we just delay that until JDK 16 
when you can remove the ContentSigner APIs, as it would be strange to 
add new methods to a deprecated class that will be marked forRemoval.

Also, why do we have to use the ContentSigner APIs for RSASSA-PSS? 
Couldn't you just use internal APIs as in your webrev?

--Sean