Allow fuel metering customization via Config::fuel_costs API

[Robbepop]

This allows to customize fuel costs for the following areas:

• Lazy translation and validation of functions.
  • For example if CompilationMode::Lazy or CompilationMode::LazyTranslation is used.
• Copying bytes or values in the following Wasm operator executions:
  • memory.{grow,copy,fill,init}
  • table.{grow,copy,fill,init}

New API

Where CustomFuelCosts is defined as:

pub struct CustomFuelCosts {
    /// The amount of bytes that can be copied for a single unit of fuel.
    pub bytes_copied_per_fuel: u32,
    /// The amount of fuel required to translate one byte from Wasm bytecode to Wasmi IR.
    pub fuel_per_bytes_translated: u32,
    /// The amount of fuel required to validate one byte of Wasm bytecode.
    pub fuel_per_bytes_validated: u32,
}

[codecov]

Codecov Report

❌ Patch coverage is 62.74510% with 19 lines in your changes missing coverage. Please review.
✅ Project coverage is 76.29%. Comparing base (ef2b908) to head (d3ca681).

Files with missing lines	Patch %	Lines
crates/core/src/fuel.rs	58.97%	16 Missing ⚠️
crates/wasmi/src/engine/config.rs	25.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2025      +/-   ##
==========================================
- Coverage   76.32%   76.29%   -0.04%     
==========================================
  Files         168      168              
  Lines       15496    15531      +35     
==========================================
+ Hits        11828    11849      +21     
- Misses       3668     3682      +14     

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