Support Wasm custom sections parsing and processing

[Robbepop]

Closes #1084.

[codecov]

Codecov Report

Attention: Patch coverage is 81.05263% with 18 lines in your changes missing coverage. Please review.

Project coverage is 80.48%. Comparing base (f1f92e4) to head (b66152b).

Files	Patch %	Lines
crates/wasmi/src/module/parser/streaming.rs	53.33%	7 Missing ⚠️
crates/wasmi/src/module/custom_section.rs	92.72%	4 Missing ⚠️
crates/wasmi/src/engine/config.rs	40.00%	3 Missing ⚠️
crates/wasmi/src/module/mod.rs	0.00%	2 Missing ⚠️
crates/wasmi/src/module/builder.rs	75.00%	1 Missing ⚠️
crates/wasmi/src/module/parser.rs	80.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1085   +/-   ##
=======================================
  Coverage   80.48%   80.48%           
=======================================
  Files         269      270    +1     
  Lines       24998    25080   +82     
=======================================
+ Hits        20119    20186   +67     
- Misses       4879     4894   +15     

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