Added F ext. instrs. to D testplan for NaNBox CPs

[coreyqh]

• Replicates F extension instructions in the D test plan to check NaNBoxing functionality, as these instructions only NaNBox when D is supported.
• cp_NaNBox ensures results are properly NaNBoxed, and cp_badNB checks behavior when an argument is not properly NaNBoxed
• Near full coverage of all duplicated instructions. One coverage hole on fsw due to cp_badNB only exercising fs1. I'll raise an issue and circle back to this soon.
• Added a trivial make_nanbox function to testgen, as instructions with only cp_nanbox do not have any tests made and miss all coverpoints. It simply writes a single random test.
• Unfortunately other instructions need these coverpoints, but we cannot presently guarantee that D is supported with the current test plan structure. For example, instructions in the ZfaF test plan can NaNBox if D is supported. Possibly we need a ZfaZfhD test plan solely for these coverpoints? Same thing Zfhmin.

[davidharrishmc]

Avoid asmcount coverpoints for the F instructions in D.
Looks like it is necessary to add ZfaZfhD and ZfhminD plans.