Grow memory on demand in FastEvaluate

[christophwille]

Doesn't work yet

MemoryTests/large_input_host_and_guest_grow_successfully fails (copy of open-policy-agent/npm-opa-wasm@f1be838#diff-a7ab91d607d5a96793af6ae3d71f8ef6e71c6ff6255438c7281c2ab7182bcaafR58)

Used approach from existing PR #36 instead of porting the JS

Error:

opa_malloc: failed
  ----> System.Exception : opa_malloc: failed
  Stack Trace:
     at Wasmtime.Function.Invoke(Span`1 argumentsAndResults, StoreContext storeContext)
   at Wasmtime.Function.InvokeWithReturn[TR](Span`1 argsAndResults, IReturnTypeFactory`1 factory, StoreContext storeContext)
   at Wasmtime.Function.<>c__DisplayClass195_0`8.<WrapFunc>b__0(T1 p0, T2 p1, T3 p2, T4 p3, T5 p4, T6 p5, T7 p6)
   at Opa.Wasm.OpaPolicy.Policy_opa_eval(Int32 entrypoint_id, Int32 dataaddr, Int32 jsonaddr, Int32 jsonlength, Int32 heapaddr) in /_/src/Opa.Wasm/OpaPolicy.Functions.cs:line 77
   at Opa.Wasm.OpaPolicy.FastEvaluate(String json, Nullable`1 entrypoint) in /_/src/Opa.Wasm/OpaPolicy.cs:line 320
   at Opa.Wasm.OpaPolicy.ExecuteEvaluate(String json, Nullable`1 entrypoint, Boolean disableFastEvaluate) in /_/src/Opa.Wasm/OpaPolicy.cs:line 283
   at Opa.Wasm.OpaPolicy.EvaluateJson(String json, Boolean disableFastEvaluate) in /_/src/Opa.Wasm/OpaPolicy.cs:line 234
   at Opa.Wasm.UnitTests.MemoryTests.large_input_host_and_guest_grow_successfully() in /home/runner/work/dotnet-opa-wasm/dotnet-opa-wasm/src/Opa.Wasm.UnitTests/MemoryTests.cs:line 38
   at System.RuntimeMethodHandle.InvokeMethod(Object target, Void** arguments, Signature sig, Boolean isConstructor)
   at System.Reflection.MethodBaseInvoker.InvokeWithNoArgs(Object obj, BindingFlags invokeAttr)
--Exception
   at Opa.Wasm.OpaPolicy.<LinkImports>b__29_0(Caller caller, Int32 addr) in /_/src/Opa.Wasm/OpaPolicy.cs:line 85
   at Wasmtime.Function.<>c__DisplayClass106_0`1.<FromCallback>b__0(IntPtr env, IntPtr callerPtr, ValueRaw* args_and_results, UIntPtr num_args_and_results)

[christophwille]

For reference https://github.com/orgs/open-policy-agent/discussions/647