Introduce ScriptTrigger & CommandsTrigger for the PHP plugin #430

Context

Part of #313. plugin-scripts wants every submodule to expose a ScriptTrigger and a CommandsTrigger, so a flow can be triggered whenever the underlying script/commands execution completes, with an exit condition deciding whether the trigger fires based on the result (e.g. only on failure).

plugin-script-php is missing both. Existing implementations in plugin-script-go, plugin-script-node, plugin-script-python, plugin-script-ruby, and plugin-script-shell (same package as the task classes, no nested subpackage) can be used as a reference.

What to implement

1. ScriptTrigger

• Triggers when io.kestra.plugin.scripts.php.Script execution completes.
• Emits an event containing: command executed, arguments, env (if available), exit code, stdout/stderr (if capture enabled), and contextual metadata (execution id, namespace, flow id).

2. CommandsTrigger

• Triggers when io.kestra.plugin.scripts.php.Commands execution completes.
• Emits an event containing: commands executed (or the matched one), exit code(s), stdout/stderr if available, and contextual metadata (execution id, namespace, flow id).

Trigger configuration requirements

Each trigger should accept at least:

• commandPattern (string / regex / glob)
• argumentsPattern (optional)
• exitCondition (string expression — can match on exit code, output, or a literal condition)

Example YAML

triggers:
  - id: on_php_fail
    type: io.kestra.plugin.scripts.php.ScriptTrigger
    commandPattern: ".*"
    exitCondition: "exitCode != 0"

triggers:
  - id: on_php_commands
    type: io.kestra.plugin.scripts.php.CommandsTrigger
    commandPattern: ".*"
    exitCondition: "exitCode == 0"