Improve Wasmi and Wasmtime API mirroring with renamings

[Robbepop]

• Config::engine_limits method -> enforced_limits
• Value enum -> Val
• ValueType enum -> ValType
• UntypedValue struct -> UntypedVal
• WasmType trait -> WasmTy
• AsContext::UserState assoc. type -> Data

[codecov]

Codecov Report

Attention: Patch coverage is 83.42665% with 148 lines in your changes are missing coverage. Please review.

Project coverage is 80.68%. Comparing base (232b95c) to head (c400242).

Files	Patch %	Lines
crates/wasmi/src/engine/translator/visit.rs	38.12%	86 Missing ⚠️
crates/cli/src/display.rs	35.71%	9 Missing ⚠️
crates/cli/src/utils.rs	0.00%	7 Missing ⚠️
crates/wasmi/src/engine/executor/instrs.rs	46.15%	7 Missing ⚠️
.../wasmi/src/engine/translator/tests/display_wasm.rs	50.00%	7 Missing ⚠️
crates/wasmi/src/table/mod.rs	54.54%	5 Missing ⚠️
crates/cli/src/main.rs	0.00%	3 Missing ⚠️
crates/wasmi/src/global.rs	72.72%	3 Missing ⚠️
crates/wasmi/src/engine/bytecode/provider.rs	0.00%	2 Missing ⚠️
crates/wasmi/src/engine/executor/instrs/binary.rs	0.00%	2 Missing ⚠️
... and 13 more

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1011      +/-   ##
==========================================
+ Coverage   80.65%   80.68%   +0.03%     
==========================================
  Files         269      269              
  Lines       24813    24775      -38     
==========================================
- Hits        20012    19990      -22     
+ Misses       4801     4785      -16     

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