[BUG][JAVA] additionalModelTypeAnnotations value is escaped

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• What's the version of OpenAPI Generator used?
• Have you search for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Bounty to sponsor the fix (example)

Description

The annotations specified with additionalModelTypeAnnotations are escaped.
Thefore, using a special character like = leads to a compilation error.

openapi-generator version

4.2.x

OpenAPI declaration file content or url

https://github.com/OpenAPITools/openapi-generator/blob/master/modules/openapi-generator-maven-plugin/examples/multi-module/sample-schema/src/main/resources/openapi.yaml

            <!-- activate the plugin -->
            <plugin>
                <groupId>org.openapitools</groupId>
                <artifactId>openapi-generator-maven-plugin</artifactId>
                <version>4.3.0-SNAPSHOT</version>
                <dependencies>
                    <dependency>
                        <groupId>${project.groupId}</groupId>
                        <artifactId>sample-schema</artifactId>
                        <version>${project.parent.version}</version>
                    </dependency>
                </dependencies>
                <executions>
                    <execution>
                        <goals>
                            <goal>generate</goal>
                        </goals>
                        <configuration>
                            <inputSpec>openapi.yaml</inputSpec>
                            <generatorName>java</generatorName>
                            <configOptions>
                                <additionalModelTypeAnnotations>@Foo(val=true)</additionalModelTypeAnnotations>
                            </configOptions>
                        </configuration>
                    </execution>
                </executions>
            </plugin>

Command line used for generation

Just run the maven plugin.

Steps to reproduce

Inside additionalModelTypeAnnotations, add a value with any special character like @Foo(val=true).

Compilation will fail becaise the annotation is written like this: @Foo(val=true)

Suggest a fix

Do not escape the value inside the template.

Start with the Maven plugin configuration in modules/openapi-generator-maven-plugin/examples/multi-module/sample-schema/src/main/resources/openapi.yaml and run the Maven plugin generation described in the issue. Trace how additionalModelTypeAnnotations reaches the Java template; done means @Foo(val=true) appears unchanged in the generated source and compiles.