Add swift package add-target-plugin command

[hi2gage]

Adds swift package add-target-plugin command for adding plugins to target from CLI

Motivation:

Featured requested in #8169

Allows users to add package plugins to targets via command line.

Forums Discussion

Modifications:

Add new add-target-plugin command which aligns with the existing add-target-dependency command

> swift package add-target-plugin --help
OVERVIEW: Add a new target plugin to the manifest

USAGE: swift package add-target-plugin <plugin-name> <target-name> [--package <package>]

ARGUMENTS:
  <plugin-name>           The name of the new plugin
  <target-name>           The name of the target to update

OPTIONS:
  --package <package>     The package in which the plugin resides
  --version               Show the version.
  -h, -help, --help       Show help information.

Result:

After running the following command:

swift package add-target-plugin OpenAPIGenerator myTarget --package swift-openapi-generator

The following addition will be made to the Package.swift manifest:

.target(
  name: "myTarget",
  plugins: [
    .plugin(name: "OpenAPIGenerator", package: "swift-openapi-generator")
  ]
)

[hi2gage]

Fixed borked tests in main

[dschaefer2]

@swift-ci please test

[dschaefer2]

@swift-ci please test self hosted windows

[bkhouri]

@swift-ci please test windows

[hi2gage]

@bkhouri is windows (non self hosted) being flakey or is this somehow related to changes I made?

It looks like #8434 passed so maybe I need rebase in the new changes?