PoC: WebAssembly API

[turbolent]

Work towards #2853

Description

This PoC explores the idea of adding a WebAssembly API to Cadence, i.e. exposing a WebAssembly VM to Cadence programs.

The PRs adds:

• A WebAssembly contract with an API inspired by the WebAssembly JavaScript Interface. The beginnings of the API support module instantiation, without imports, and access to function exports with i32 and i64 types.

• An implementation of the WebAssembly API based on wasmtime. The VM has been configured with some reasonable settings and limits, but need to be refined.

• A test case which demonstrates loading a simple add (i32, i32) -> i32 function, calling it with Cadence UInt32 values, and getting back the result as a Cadence UInt32.

  https://github.com/onflow/cadence/pull/2760/files#diff-27b18491bc5b8a8ea5aabf7d9453695aef776c0858db4c84eea0963717c296b5R201-R216

---

• Targeted PR against master branch
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work
• Code follows the standards mentioned here
• Updated relevant documentation
• Re-reviewed Files changed in the Github PR explorer
• Added appropriate labels

[github-actions]

Cadence Benchstat comparison

This branch with compared with the base branch onflow:master commit a56e521
The command for i in {1..N}; do go test ./... -run=XXX -bench=. -benchmem -shuffle=on; done was used.
Bench tests were run a total of 7 times on each branch.

Collapsed results for better readability

[codecov]

Codecov Report

Attention: Patch coverage is 79.34272% with 88 lines in your changes missing coverage. Please review.

Project coverage is 80.33%. Comparing base (aeef038) to head (12b56a5).

❗ Current head 12b56a5 differs from pull request most recent head e55b81e

Please upload reports for the commit e55b81e to get more accurate results.

Files	Patch %	Lines
runtime/webassembly.go	70.10%	45 Missing and 10 partials ⚠️
runtime/stdlib/webassembly.go	80.16%	16 Missing and 8 partials ⚠️
runtime/repl.go	0.00%	4 Missing ⚠️
runtime/environment.go	83.33%	2 Missing and 1 partial ⚠️
runtime/common/computationkind_string.go	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2760      +/-   ##
==========================================
- Coverage   80.33%   80.33%   -0.01%     
==========================================
  Files         390      393       +3     
  Lines       95921    96338     +417     
==========================================
+ Hits        77060    77390     +330     
- Misses      16138    16206      +68     
- Partials     2723     2742      +19     

Flag	Coverage Δ
unittests	80.33% <79.34%> (-0.01%)	⬇️

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[PratikDhanave]

hi @turbolent thank you for adding a WebAssembly API to Cadence.
I want to know that next task would exposing wasmtime type table ?