Fix fast 1-weso parameter approximation, for massive speedup

[xearl4]

The "fast" 1-Wesolowski prover inadvertently mixed up parameters in the call to ApproximateParameter.

ApproximateParameter's signature has L followed by K:

void ApproximateParameters(uint64_t T, uint32_t& L, uint32_t& K)

However, the 1-Weso calls used K followed by L:

ApproximateParameters(num_iterations, k, l);

While this typo does not affect the correctness of the created 1-Weso proof, this causes 1-Weso proving to be much slower than necessary. In isolated testing, the 1-Weso proof generation is up to 10x slower.

Funnily enough, the "slow" VDF impl (in src/provers_slow.h) uses a separate 1-Weso prover implementation which doesn't suffer from this bug, thus making the "slow" VDF impl faster than the "fast" overall.

To be clear: the fixed bug only affects the performance (not the correctness!) of computing 1-Weso proofs (thus, blueboxing) using the "fast" implementation. Regular software timelords (N-Weso), hardware (ASIC) timelords, and the "slow" bluebox implementation are unaffected.

The speedup can be observed/tested by running src/1weso_test.cpp:

$ hyperfine --warmup 5 "./1weso_test.orig" "./1weso_test.fixed"
Benchmark 1: ./1weso_test.orig
  Time (mean ± σ):     17.250 s ±  1.153 s    [User: 23.946 s, System: 0.037 s]
  Range (min … max):   15.582 s … 18.372 s    10 runs

Benchmark 2: ./1weso_test.fixed
  Time (mean ± σ):      8.746 s ±  0.010 s    [User: 14.651 s, System: 0.029 s]
  Range (min … max):    8.733 s …  8.765 s    10 runs

Summary
  ./1weso_test.fixed ran
    1.97 ± 0.13 times faster than ./1weso_test.orig

1weso_test also confirms that 1-Weso proof correctness is unaffected by this change. The prover still generates the exact same proofs, it just does so much faster.

[wjblanke]

Many thanks!