Set custom program name for the built-in LSP server

This PR sets custom program name for the built-in LSP server.

Before:

```console
$ ps aux | grep rubocop
user  17414  0.0  0.2  5557716 144376  ??  Ss  4:48PM  0:02.13 /Users/user/.rbenv/versions/3.2.2/lib/ruby/gems/3.2.0/bin/rubocop --lsp
```

After:

```console
$ ps aux | grep 'rubocop'
user  17414  0.0  0.2  5557716 144376  ??  Ss  4:48PM  0:02.13 rubocop --lsp /Users/user/src/github.com/rubocop/rubocop
```

When searching for the LSP server process, it is helpful to display the path to the project root instead of the Ruby command path.
This approach is already being implemented in server mode:
https://github.com/rubocop/rubocop/blob/v1.63.2/lib/rubocop/server/core.rb#L31

changelog/change_set_custom_program_name_for_the_builtin_lsp_server.md

@@ -0,0 +1 @@
+* [#12855](https://github.com/rubocop/rubocop/pull/12855): Set custom program name for the built-in LSP server. ([@koic][])

docs/modules/ROOT/pages/usage/lsp.adoc

@@ -254,8 +254,8 @@ Run `rubocop --lsp` command from LSP client.
 When the language server is started, the command displays the language server's PID:
 
 ```console
-$ ps aux | grep rubocop
-user             17414   0.0  0.2  5557716 144376   ??  Ss    4:48PM   0:02.13 /Users/user/.rbenv/versions/3.2.2/lib/ruby/gems/3.2.0/bin/rubocop --lsp
+$ ps aux | grep 'rubocop --lsp'
+user             17414   0.0  0.2  5557716 144376   ??  Ss    4:48PM   0:02.13 rubocop --lsp /Users/user/src/github.com/rubocop/rubocop
 ```
 
 NOTE: `rubocop --lsp` is for starting LSP client, so users don't manually execute it.

lib/rubocop/lsp/server.rb

@@ -21,6 +21,8 @@ module LSP
     # @api private
     class Server
       def initialize(config_store)
+        $PROGRAM_NAME = "rubocop --lsp #{ConfigFinder.project_root}"
+
         RuboCop::LSP.enable
 
         @reader = LanguageServer::Protocol::Transport::Io::Reader.new($stdin)