Give the command palette revalidation commands a different name from the language server command

[datho7561]

lemminx registers the commands:

• xml.validation.current.file
• xml.validation.all.files
  for retriggering validation on a file when the schema has changed.

vscode-xml also registers commands with the same names that delegate to the lemminx commands. These commands are the ones that appear in the VS Code command palette. In order to delegate to the lemminx commands, the VS Code extension needs to use the EXECUTE_WORKSPACE_COMMAND to specify that the server command should be used.

Instead of using EXECUTE_WORKSPACE_COMMAND, we could call the server validation commands directly if we name the client commands differently. Renaming the client commands will also prevent an error about registering the same command twice from appearing in the debug logs.

Rename the client commands so that the names don't clash and change the client command implementation to invoke the server commands directly.