Add a function to purge unused configs

[dachengx]

What is the problem / what does the code in this PR do

Sometimes we see a lot of warnings from

strax/strax/context.py

Line 723 in 0f36687

self.log.warning(f"Option {k} not taken by any registered plugin")

because some unnecessary configs are set. Examples: https://xenonnt.slack.com/archives/C016DM0JPK9/p1702545417958799 and https://xenonnt.slack.com/archives/C016DM0JPK9/p1705510467687369.

WARNING:strax:Option check_raw_record_overlaps not taken by any registered plugin
WARNING:strax:Option gain_model not taken by any registered plugin
WARNING:strax:Option gain_model_nv not taken by any registered plugin
...

Can you briefly describe how it works?

This PR provides a function to purge those configs. But be cautious with it! Only use it when you stop registering more new plugins.

Can you give a minimal working example (or illustrate with a figure)?

Please include the following if applicable:

• Update the docstring(s)
• Update the documentation
• Tests to check the (new) code is working as desired.
• Does it solve one of the open issues on github?

Please make sure that all automated tests have passed before asking for a review (you can save the PR as a draft otherwise).

[coveralls]

coverage: 91.502% (+0.03%) from 91.47%
when pulling 31cf51b on remove_configs
into ff81edb on master.

[yuema137]

Looks good to me as it provides an option for users to clean up the config.

[dachengx]

Before this PR:

After this PR: