Parent issue: #19604

Description

Add Checkstyle checks for all rules under §3.3 - Import statements of the OpenJDK Java Style Guidelines v6.

Rules covered

From §3.3 - Import statements:

1. Import statements should be sorted primarily by non-static / static with non-static imports first, secondarily by package origin (java → javax → external → internal), and tertiary by package and class identifier in lexicographical order. - ImportOrder Check
2. Import statements should not be line wrapped, regardless of whether it exceeds the recommended maximum length of a line. - NoLineWrap Check
3. No unused imports should be present. - UnusedImports Check

Checks to add to openjdk_checks.xml

TreeWalker-level:

<module name="ImportOrder">
  <property name="groups" value="java,javax,org,com"/>
  <property name="ordered" value="true"/>
  <property name="separated" value="true"/>
  <property name="option" value="bottom"/>
  <property name="sortStaticImportsAlphabetically" value="true"/>
</module>

<module name="NoLineWrap">
  <property name="tokens" value="IMPORT, STATIC_IMPORT"/>
</module>

<module name="UnusedImports"/>

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