Fix AbstractJavaCodegen ability to customize container types

Created by: dmivankov

Fix for https://github.com/OpenAPITools/openapi-generator/issues/13549

After https://github.com/OpenAPITools/openapi-generator/pull/5466 java codegen emits Set for array with uniqueItems=true which has its downsides

• easy to lose track of element order (it can be important)
• easy to lose ordering by switching between java Set flavors (HashSet vs LinkedHashSet) somewhere down the line
• bigger divergence from original json types (either array or object)

Luckily types can be customized/overriden by extending the generator:

• extend JavaClientCodegen for example
• in constructor do

    super();
    // import/interface type
    typeMapping().put("set", typeMapping().get("array"));
    // concrete type
    instantiationTypes().put("set", instantiationTypes().get("array"));

But sometimes it won't work because of missing ArrayList import, can be fixed by also doing

    // workaround for https://github.com/OpenAPITools/openapi-generator/issues/13549
    // to be fixed in https://github.com/OpenAPITools/openapi-generator/pull/13550
    importMapping().put("LinkedHashSet", importMapping().get("ArrayList"));

Looks like a bug of assuming "set" fields are instantiated with LinkedHashSet, let's fix it by using type mappings.

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