gh-119109: functools.partial.fallforward fix

[dg-pb]

#119109

I went with option 1. It is cleaner, faster and has a natural flow.

Before:

fromfunctoolsimportpartialdeffunc(a, b, c=0):
returna-b-cp1=partial(func, 1)
print(p1(2)) # -1%timeitp1(2) # 100 nsp1.keywords['c'] =1print(p1(2)) # -2%timeitp1(2) # 234 nsdelp1.keywords['c']
print(p1(2)) # -1%timeitp1(2) # 144 ns

After:

p1=partial(func, 1)
print(p1(2)) # -1%timeitp1(2) # 100 nsp1.keywords['c'] =1print(p1(2)) # -2%timeitp1(2) # 234 nsdelp1.keywords['c']
print(p1(2)) # -1%timeitp1(2) # 100 ns

• Issue: functools.partial does not re-set vector call. #119109