feat: add hook for Enum.valueOf

[onionpsy]

Add a hook to guide Enum.valueOf toward a valid enum name by deterministically picking a single candidate from the enum list

[fmeum]

This can jump around when candidate changes slightly, which could throw off the guidance. Instead, you could use a ClassValue to associate an Enum class with a sorted array of its values and then Arrays.binarySearch for the nearest valid value (perhaps ignoring case).

[oetr]

I am curious about the reasoning to go for the nearest enum value--why prefer it over any other enum value?

I am asking because I think there is a bias in libfuzzer's output (e.g. zeros are way more favored than anything else), and by taking the closest value, this bias gets propagated. WDYT?

[fmeum]

Picking the nearest candidate isn't necessary, but I think that a particular guideTowardsEquality call (with a fixed hook id) should keep guiding towards the same target as long as the fuzzer keeps making progress towards the target tracked in the last iteration. I could see the behavior becoming erratic if the target changes as more bytes agree.

[onionpsy]

I benchmarked the 3 solutions (binary search, random pick, hashcode based pick) by executing 50 times a fresh fuzz test with 1M executions.
It seems like distribution is slightly more spread in the binary search but not by a large margin. On the other hand it does increases the complexity.

Binary search with random pick for the neighbour:

SUPER_SECRET_SHADE   hits=76401   
YELLOW               hits=191745  
BBB                  hits=584921  
CCC                  hits=484576  
DDD                  hits=480848  
EEE                  hits=514521  
Total hits across all enum constants: 2333012

Hashcode pick (random pick has also very similar values):

SUPER_SECRET_SHADE   hits=66965   
YELLOW               hits=163662  
BBB                  hits=556240  
CCC                  hits=547206  
DDD                  hits=541491  
EEE                  hits=536563  
Total hits across all enum constants: 2412127