Plugins support embracing modular architecture

[rishabhmaurya]

Meta task to migrate plugin framework to use new proposed modular architecture.

It aims towards solving following limitation in OpenSearch plugin framework -

1. Plugin should depend on sub-modules of concern instead of depending on uber server module. This will improve overall tech debts on maintenance of plugin, codebase hygiene, new plugin development and productivity, lesser breaking changes with major version upgrades of OpenSearch. Also, if there are no changes in minor version upgrade of any of the dependencies then plugins can remain unchanged and just continue to work. Un-modularized code is the major reason why so many plugins becomes stagnant with OpenSearch version upgrades, which forces plugin developers to update to the new version irrespective of what has changed.
2. Dynamic installation of plugins whenever possible.

• Reimplement PluginService to incorporate new modular architecture
• PluginService should make use of new ModuleLayer explicitly for all plugins. It can also be used to load new plugins dynamically.
• Migrate existing plugins in opensearch codebase to new architecture

Please add any other pain points with respect to plugin development, maintenance, installation and administration.