Fix learning method matches for the detected events

[syncpark]

In src/event.rs, the learning methods are defined as follows:

/// in src/event.rs
/// Machine Learning Method.
#[derive(Clone, Copy, Eq, PartialEq, Deserialize, Serialize)]
pub enum LearningMethod {
    Unsupervised,
    SemiSupervised,
}

After the EventCategory::HttpThreat is replaced to EventCategory::Reconnaissance, the following code in src/event/common.rs may return incorrect results.

review-database/src/event/common.rs

Lines 163 to 172 in 2eda8f9

	if let Some(learning_methods) = &filter.learning_methods {
	let category = self.category();
	if learning_methods.iter().all(|learning_method| {
	let unsuper = matches!(*learning_method, LearningMethod::Unsupervised);
	let http = matches!(category, EventCategory::Reconnaissance);
	unsuper && !http || !unsuper && http
	}) {
	return Ok((false, None));
	}
	}

Tasks:

• The matching code must be modified to return correct results.
• And the learning methods of the detected events need to be assigned when the detected events are generated.

[syncpark]

To solve this issue, all event structures must contain LearningMethod value and implement learning_method() function.