[Swift4] fix multi thread issue

Description

The generated AlamofireImplementations.swift file has a non thread-locked dictionary to save session managers. Accessing this dictionary from multiple threads at the same times causes a crash. Not all versions of this file in the file tree has a defect implementation. Simply copy a fixed version to all non fixed versions will fix this issue.

Some implementation of this file in the Swift 5 generator also needs a fix.

Swagger-codegen version

3.0.14

Command line used for generation

swagger-codegen generate -l swift4 -DprojectName=FolderService -i swagger.json -o folder --model-name-prefix "FolderService"

Steps to reproduce

Generate swift 4 code with v 3.0.14 installed via Homebrew.

Related issues/PRs

#3873 #8583 #5610

Suggest a fix/enhancement

Copy solution from fixed implementations of the AlamofireImplementations.swift
https://github.com/swagger-api/swagger-codegen/blob/master/modules/swagger-codegen/src/main/resources/swift4/AlamofireImplementations.mustache

Start with modules/swagger-codegen/src/main/resources/swift4/AlamofireImplementations.mustache and compare it with the fixed implementations referenced in the issue. Check the other Swift 4 and Swift 5 generator templates that produce AlamofireImplementations.swift, then run the provided swagger-codegen command to verify generated clients no longer use the defective session-manager dictionary implementation.