refactor: rename CLI "plugin" command to "app" (#3662)

* refactor: rename "plugin" to "app"

* refactor: simplify code

* chore: update changelog

* tests: fixed unit tests

* tests: fix integration tests

* chore: change plugin template to use `app` as the type name

* chore: update plugin code documentation to use "app" instead

* tests: fixed service unit tests

* chore: update comments

* chore: fix typo

* chore: improve command description

* chore: restore plugin to test case names

* chore: remove commented unit test code

* chore: change app commands to properly set example command

Co-authored-by: Julien Robert

* chore: remove redundant plugin path check

changelog.md

@@ -17,6 +17,7 @@
 - [#3658](https://github.com/ignite/cli/pull/3658) Rename Marshaler to Codec in EncodingConfig
 - [#3653](https://github.com/ignite/cli/pull/3653) Add "app" extension to plugin binaries
 - [#3656](https://github.com/ignite/cli/pull/3656) Disable Go toolchain download
+- [#3662](https://github.com/ignite/cli/pull/3662) Refactor CLI "plugin" command to "app"
 - [#3669](https://github.com/ignite/cli/pull/3669) Rename `plugins` config file to `igniteapps`
 
 ### Fixes

ignite/cmd/cmd.go

@@ -39,8 +39,8 @@ const (
 )
 
 // New creates a new root command for `Ignite CLI` with its sub commands.
-// Returns the cobra.Command, a cleanUp function and an error. The cleanUp
-// function must be invoked by the caller to clean eventual plugin instances.
+// Returns the cobra.Command, a cleanup function and an error. The cleanup
+// function must be invoked by the caller to clean eventual Ignite App instances.
 func New(ctx context.Context) (*cobra.Command, func(), error) {
 	cobra.EnableCommandSorting = false
 
@@ -78,14 +78,14 @@ To get started, create a blockchain:
 		NewTools(),
 		NewDocs(),
 		NewVersion(),
-		NewPlugin(),
+		NewApp(),
 		NewDoctor(),
 	)
 	c.AddCommand(deprecated()...)
 
 	// Load plugins if any
 	if err := LoadPlugins(ctx, c); err != nil {
-		return nil, nil, fmt.Errorf("error while loading plugins: %w", err)
+		return nil, nil, fmt.Errorf("error while loading apps: %w", err)
 	}
 	return c, UnloadPlugins, nil
 }