add support for configuring log level using custom rules

[Loori-R]

Summary

This pull request adds a "Log level rules" section to the datasource configuration screen. It allows users to define custom rules for dynamically assigning log levels based on field values.

Related issue: #294, #209, #201

How it works

Click "Add rule" to create a new rule. Each rule consists of the following elements:

1. Enable switch – toggle to enable or disable the rule.
2. Field name – the log field the rule applies to.
3. Operator – condition type: Equals, Not equal, Matches regex, Less than, Greater than.
4. Value – the value to compare against.
5. Log level – level to assign if the rule matches: critical, warning, error, info, debug, trace, unknown.
6. Delete button – removes the rule.

After adding or editing rules, make sure to click "Save & test" to apply the updated configuration.

Rule priority

If multiple rules match, the first one in the list takes precedence.