[BUG]Names don't adhere to plugin naming convention

[mnkugler]

What is the bug?
Align all names to the convention:
https://github.com/opensearch-project/opensearch-plugins/blob/main/CONVENTIONS.md#opensearch-plugins

We should adjust the folder and move build.gradle, etc. to the root folder of the repo.

opensearchplugin metadata is missing from build.gradle

Do you have any additional context?
Referred to here:
opensearch-project/opensearch-plugins#174

[VijayanB]

plugin's build.gradle is at https://github.com/opensearch-project/geospatial/blob/main/build.gradle ( root of repository )
It also contains plugin's metadata and follows plugin's naming convention.