[typescript] typescript client generator supports import mapping

Created by: uesyn

typescript-node client generator supports import mapping, but typescript client generator doesn't. This PR makes typescript client generator support import mapping feature.

I verified that import mapping works correctly in the following way.

• ./bin/generate-samples.sh generates no changes because which doesn't use import mapping.
• Generate sample codes with import-mapping.

$ java -jar ./modules/openapi-generator-cli/target/openapi-generator-cli.jar generate -g typescript --import-mappings=Tag="../../types" -o out -i https://raw.githubusercontent.com/openapitools/openapi-generator/master/modules/openapi-generator/src/test/resources/3_0/petstore.yaml --additional-properties=useInversify=true

$ grep -1 -r "../../types" out
out/models/ObjectSerializer.ts-export * from './Pet';
out/models/ObjectSerializer.ts:export * from '../../types';
out/models/ObjectSerializer.ts-export * from './User';
--
out/models/ObjectSerializer.ts-import { Pet     , PetStatusEnum   } from './Pet';
out/models/ObjectSerializer.ts:import { Tag } from '../../types';
out/models/ObjectSerializer.ts-import { User } from './User';
--
out/models/all.ts-export * from './Pet'
out/models/all.ts:export * from '../../types'
out/models/all.ts-export * from './User'
--
out/models/Pet.ts-import { Category } from './Category';
out/models/Pet.ts:import { Tag } from '../../types';
out/models/Pet.ts-import { HttpFile } from '../http/http';
--
out/services/ObjectParamAPI.ts-import type { Pet } from '../models/Pet';
out/services/ObjectParamAPI.ts:import type { Tag } from '../../types';
out/services/ObjectParamAPI.ts-import type { User } from '../models/User';
--
out/services/ObservableAPI.ts-import { Pet } from "../models/Pet";
out/services/ObservableAPI.ts:import { Tag } from "../../types";
out/services/ObservableAPI.ts-import { User } from "../models/User";
--
out/services/PromiseAPI.ts-import { Pet } from "../models/Pet";
out/services/PromiseAPI.ts:import { Tag } from "../../types";
out/services/PromiseAPI.ts-import { User } from "../models/User";
--
out/types/ObjectParamAPI.ts-import { Pet } from '../models/Pet';
out/types/ObjectParamAPI.ts:import { Tag } from '../../types';
out/types/ObjectParamAPI.ts-import { User } from '../models/User';
--
out/types/ObservableAPI.ts-import { Pet } from '../models/Pet';
out/types/ObservableAPI.ts:import { Tag } from '../../types';
out/types/ObservableAPI.ts-import { User } from '../models/User';
--
out/types/PromiseAPI.ts-import { Pet } from '../models/Pet';
out/types/PromiseAPI.ts:import { Tag } from '../../types';
out/types/PromiseAPI.ts-import { User } from '../models/User';

close: https://github.com/OpenAPITools/openapi-generator/issues/12907

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