Support variables in Filter Rows values

[Wassim67]

Allow Filter Rows condition constants to use Hop variables.

At runtime, the transform now clones its configured condition and resolves variables in constant values recursively. The original metadata remains unchanged, so expressions such as ${FILTER_VALUE} are preserved in the pipeline definition.

The Filter Rows dialog also passes its variable context to the condition value editor. This enables the standard TextVar variable indicator and selector. Typed values are resolved for validation while the variable expression itself is kept for serialization.

Tests cover:

• String
• Integer
• Number
• BigNumber
• Boolean
• Date
• Timestamp
• regular expressions
• nested conditions
• preservation of the original metadata
• matching and non-matching values

Validation performed:

• ./mvnw -pl :hop-transform-filterrows -am -DskipTests compile
• ./mvnw -pl :hop-transform-filterrows -DskipITs test (11 tests, 0 failures)
• ./mvnw -pl :hop-ui,:hop-transform-filterrows apache-rat:check

---

Thank you for your contribution! Follow this checklist to help us incorporate your contribution quickly and easily:

• Run mvn clean install apache-rat:check to make sure basic checks pass. A more thorough check will be performed on your pull request automatically.
• If you have a group of commits related to the same change, please squash your commits into one and force push your branch using git rebase -i.
• Mention the appropriate issue in your description (for example: addresses #123), if applicable.

To make clear that you license your contribution under the Apache License Version 2.0, January 2004
you have to acknowledge this by using the following check-box.

• I hereby declare this contribution to be licensed under the Apache License Version 2.0, January 2004
• In any other case, please file an Apache Individual Contributor License Agreement.