[FEATURE] Split PPL tool into two tools for generate and execute

[joshuali925]

Is your feature request related to a problem?
The current PPL tool implementation will execute PPL as well

skills/src/main/java/org/opensearch/agent/tools/PPLTool.java

Line 172 in e278d8d

PPLQueryRequest pplQueryRequest = new PPLQueryRequest(ppl, jsonContent, null, "jdbc");

This can be useful for chat, where it would need the query response to reply to the user. But for query assist in event analytics observability plugin, the PPL tool is only used to generate the query, execution will be covered by event analytics. This allows UI to make any additional modifications to the query. It's ok to just ignore PPL execution results from PPL tool, but it's extra overhead and a bit unreliable since sometimes we need to extract the original PPL from error messages

skills/src/main/java/org/opensearch/agent/tools/PPLTool.java

Line 187 in e278d8d

String pplError = "execute ppl:" + ppl + ", get error: " + e.getMessage();

What solution would you like?
Split PPL tool into two parts, one for generate, one for execute

What alternatives have you considered?
A clear and concise description of any alternative solutions or features you've considered.

Do you have any additional context?
cc @xinyual

[xinyual]

Add one more field to solve this issue. Pass "execute": false when you register Tool

[joshuali925]

thanks