* Implement ext_ hashes for contracts (issue #5258)
* load cryto hash .wat from raw string literal instead of file
* update .wat contents for testing crypto hashes
* remove unnecessary 'static
* fix bug in input (call_indirect required 1+ at least it seems)
* no longer use scratch buffer for crypto hash functions
* improve doc comments of ext_ hash functions
* remove unnecessary comment in .wat test file
* add return value (const 0) to contract test to hopefully enable result buffer
* fix bug in contract assertion
* implement proper output_len in contract
* implement proper test for crypto hashes
* bump spec_version 238 -> 239
* fix COMPLEXITY description
* remove final invalid instances of scratch buffer from docs