Implement EngineLimits for Wasmi

[Robbepop]

Closes #980.

This initial implementation does not allow full customization of the EngineLimits type and only offers two modes:

• EngineLimits::default: disables all limits (as it is now)
• EngineLimits::strict: enables strict limits to prevent malicious inputs from taking major effect

In later revisions we might allow users to partially or fully customize the EngineLimits but for now we keep it as a black box.

Enabled via:

let mut config = wasmi::Config::default();
config.engine_limits(wasmi::EngineLimits::strict());

@athei I hope this implementation is black boxy enough for your likes.

[codecov]

Codecov Report

Attention: Patch coverage is 76.84729% with 47 lines in your changes are missing coverage. Please review.

Project coverage is 81.84%. Comparing base (48d5fb2) to head (2079f1c).

Files	Patch %	Lines
crates/wasmi/src/engine/limits/engine.rs	0.00%	30 Missing ⚠️
crates/wasmi/src/module/parser.rs	73.58%	14 Missing ⚠️
crates/wasmi/src/engine/config.rs	66.66%	2 Missing ⚠️
crates/wasmi/src/error.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #985      +/-   ##
==========================================
- Coverage   81.87%   81.84%   -0.04%     
==========================================
  Files         260      262       +2     
  Lines       23904    24102     +198     
==========================================
+ Hits        19572    19726     +154     
- Misses       4332     4376      +44     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.