perf(translator): increase performance

[pythonbrad]

Description

• This commit reduces memory allocations as possible.

Related issues

• impact of rhai in the Translator performance #200
• need of reviewers #57

Changes

• Stored Engine in the structure Translator reducing the construction and discarding of the rhai runtime on every translate call.
• Eliminated Predicate construction before condition is checked.
• Fixed a bug in the building of the remaining_code.
• Replaced sort_by by sort_unstable_by to reduce memory usage.

Additional changes

Fixed potential panic in the comparison between the first characters.

Dataset

// Prepares the dictionary.
let mut dictionary = IndexMap::new();
dictionary.insert("jump".to_string(), vec!["sauter".to_string()]);
// Why a user want to do it? 
dictionary.insert("😎".to_string(), vec!["cool".to_string()]);

Error

thread 'main' (103661) panicked at engine/translator/src/lib.rs:345:75:
end byte index 1 is not a char boundary; it is inside '😎' (bytes 0..4 of string)
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace