Add an anchor to each option on keytool man page

Providing anchors for each option on the keytool man page can help when needing to reference an option from external documentation or content.

The javac page already does this: https://docs.oracle.com/en/java/javase/18/docs/specs/man/javac.html#option-class-path

Following its precedent and for consistency the anchors should follow the option-[option-name-in-lower-case] format, e.g. option-gencert.

For non-URL compliant characters in an option, if applicable, should be replaced with a `-`.