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### What

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obvious)? -->

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Earlier, for pre-response plugins, a span is emitted for each plugin
execution. This PR wraps all plugin executions in a new span that
extends the client headers as parent context.

Before:

![main_pre_resp_plugins](https://github.com/user-attachments/assets/a3d74498-3f56-48fc-becf-a04b814aee4c)
After:

![refactors_pre_resp_plugins](https://github.com/user-attachments/assets/9277327f-a8de-419c-8423-e662ae09c3b0)

Note: `pre_response_plugins_execute` span name renamed to
`execute_all_pre_response_plugins` in later commits.
### How

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steps)? -->
Move execution of pre-response plugins in a task, into a new function.
Create a span that wraps a function that executes all plugins async.

V3_GIT_ORIGIN_REV_ID: a1febecf4b429e1441e4b53a9b32f39519a12ba9