Align gen_ai.tool_definitions with JSON Schema and add it to completion hook (#4181)

* add gen_ai.tool_definitions to completion hook

* hash tool defintions

* Update CHANGELOG

* make tool.defintions optional in on_completion

* fix lint errors

* add gen_ai.tool_definitions to completion hook

* hash tool defintions

* fix CompetionHook docstring

* fix lint test

* add gen_ai.tool_definitions to completion hook

* hash tool defintions

* Update CHANGELOG

* align tool.defintions with JSON schema

* fix tests

* fix ruff

* fix unexpected indent

* use local changes from util/opentelemetry-util-genai

* fix ruff

* add gen_ai.tool_definitions to completion hook

* re-add changes lost during merge

* put tool.defintions in the telemetry by default and the params behind the flag

* fix: Too many local variables

* address comments

* Add comments to udpate of util-genai version after release

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Co-authored-by: Aaron Abbott <aaronabbott@google.com>