Swift4: Update samples using latest codegen and templates

[ehyche]

PR checklist

• [x ] Read the contribution guidelines.
• [ x] Ran the shell script under ./bin/ to update Petstore sample so that CIs can verify the change. (For instance, only need to run ./bin/{LANG}-petstore.sh and ./bin/security/{LANG}-petstore.sh if updating the {LANG} (e.g. php, ruby, python, etc) code generator or {LANG} client's mustache templates). Windows batch files can be found in .\bin\windows\.
• [x ] Filed the PR against the correct branch: 3.0.0 branch for changes related to OpenAPI spec 3.0. Default: master.
• [x ] Copied the technical committee to review the pull request if your PR is targeting a particular programming language.

Description of the PR

There are a plethora of swift4--.sh script files, and so sometimes not all of the samples get updated each time a PR is submitted. So this change:

• Creates a single bin/swift4-all.sh which runs ALL of the applicable configurations (default, rxswift, promisekit, objcCompatible) against ALL of the applicable specs.
• Re-generates all of the samples/client/petstore/swift4/* and samples/client/test/swift4/* generated code.

There are NO changes to the codegen module or the templates in this change - just keeping the samples up-to-date.