Add `rescan` option to JFrogBuildScan task

The JFrogBuildScan@1 task does not currently expose JFrog CLI's --rescan option.

This would be useful when a build has already been successfully scanned and needs to be scanned again, for example after an Xray ignore rule has been added or changed.

It is also relevant for pipelines where the build is scanned during CI but deployment takes place significantly later. In that case, teams may want to explicitly rescan the same build as part of the deployment process rather than rely solely on the earlier scan result.

Could a rescan boolean input/checkbox be added to the task, defaulting to false?

For example:

- task: JFrogBuildScan@1
  inputs:
    xrayConnection: 'jfrog xray token'
    buildName: '$(Build.DefinitionName)'
    buildNumber: '$(Build.BuildNumber)'
    allowFailBuild: true
    vuln: false
    rescan: true

This would pass the equivalent of --rescan to the underlying jf build-scan command.

A dedicated boolean input seems preferable to a generic arguments field, as --rescan is a specific option of the Build Scan command and can be clearly exposed through both the task UI and YAML.

Start at the JFrogBuildScan@1 task definition and trace how its inputs reach the underlying jf build-scan invocation. Add the rescan boolean with a false default, expose it in the task UI and YAML, and verify that enabling it passes --rescan.