[BUG][JAVA] Setting generateAliasAsModel to true breaks compilation due to missing type HashMap

Created by: tigerinus

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
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Description

openapi-generator version

5.3.0

OpenAPI declaration file content or url

https://newpathfly.ticketcombine.com/openapi.yaml

Generation Details

            <plugin>
                <groupId>org.openapitools</groupId>
                <artifactId>openapi-generator-maven-plugin</artifactId>
                <version>5.3.0</version>
                <executions>
                    <execution>
                        <id>1</id>
                        <goals>
                            <goal>generate</goal>
                        </goals>
                        <configuration>
                            <inputSpec>https://newpathfly.ticketcombine.com/openapi.yaml</inputSpec>
                            <generatorName>java</generatorName>
                            <apiPackage>com.newpathfly.api</apiPackage>
                            <modelPackage>com.newpathfly.model</modelPackage>
                            <skipIfSpecIsUnchanged>true</skipIfSpecIsUnchanged>
                            <generateAliasAsModel>true</generateAliasAsModel>
                            <configOptions>
                                <dateLibrary>java8</dateLibrary>
                                <library>webclient</library>
                                <openApiNullable>false</openApiNullable>
                                <serializableModel>true</serializableModel>
                                <performBeanValidation>true</performBeanValidation>
                                <useBeanValidation>true</useBeanValidation>
                                <useGzipFeature>true</useGzipFeature>
                            </configOptions>
                        </configuration>
                    </execution>
                </executions>
            </plugin>

Steps to reproduce

1. Clone https://github.com/newpathfly/newpathfly-public-sdk
2. Update pom.xml with and without generateAliasAsModel set to true
3. open any source that references HashMap, e.g. target/generated-sources/openapi/src/main/java/com/newpathfly/model/Check.java in IDE, like VSCode.

Expect: HashMap type is imported

import java.util.HashMap;

Actual: HashMap type is not imported

Related issues/PRs

Suggest a fix