Solution for skills listing view addressed in
elastic/search-team#13362

## Summary

This PR adds a new Skills page for the chosen agent. 

Notes:
- In built capabilties are toggled at an agent level and inject/remove
skills to a specific agent
- If in built skills are enabled, then they are displayed and
non-editable for that specific agent
- If disabled, in built skilsl can be added manually to the agent
- In built skills are not editable from agent specific UX
- When new skill is created it is auto added to the global config but
also enabled for the current selected agent.




https://github.com/user-attachments/assets/23664498-51c3-4bef-bad3-136aaa90d276

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Co-authored-by: kibanamachine <42973632+kibanamachine@users.noreply.github.com>

Solution for plugins listing view addressed in
elastic/search-team#13362

## Summary

This PR adds a new Plugins page for the chosen agent. Agent > Customize
> Plugins



https://github.com/user-attachments/assets/9c12c2f8-01d6-4fcb-8f73-43b15f75760e

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Co-authored-by: Elastic Machine <elasticmachine@users.noreply.github.com>

Closes elastic/search-team#13479

## Summary

This PR adds a new Tool page for the chosen agent. Agent > Customize >
Advanced > Tool




https://github.com/user-attachments/assets/51fc947b-2a90-4334-9274-54739c2e1ce7

---------

Co-authored-by: kibanamachine <42973632+kibanamachine@users.noreply.github.com>

## Summary

Design tweaks to match figma



https://github.com/user-attachments/assets/97a046cc-f79e-49cf-b1ce-f3f5158af9d7

## Summary

Summarize your PR. If it involves visual changes include a screenshot or
gif.


### Checklist

Check the PR satisfies following conditions. 

Reviewers should verify this PR satisfies this list as well.

- [ ] Any text added follows [EUI's writing
guidelines](https://elastic.github.io/eui/#/guidelines/writing), uses
sentence case text and includes [i18n
support](https://github.com/elastic/kibana/blob/main/src/platform/packages/shared/kbn-i18n/README.md)
- [ ]
[Documentation](https://www.elastic.co/guide/en/kibana/master/development-documentation.html)
was added for features that require explanation or tutorials
- [ ] [Unit or functional
tests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)
were updated or added to match the most common scenarios
- [ ] If a plugin configuration key changed, check if it needs to be
allowlisted in the cloud and added to the [docker
list](https://github.com/elastic/kibana/blob/main/src/dev/build/tasks/os_packages/docker_generator/resources/base/bin/kibana-docker)
- [ ] This was checked for breaking HTTP API changes, and any breaking
changes have been approved by the breaking-change committee. The
`release_note:breaking` label should be applied in these situations.
- [ ] [Flaky Test
Runner](https://ci-stats.kibana.dev/trigger_flaky_test_runner/1) was
used on any tests changed
- [ ] The PR description includes the appropriate Release Notes section,
and the correct `release_note:*` label is applied per the
[guidelines](https://www.elastic.co/guide/en/kibana/master/contributing.html#kibana-release-notes-process)
- [ ] Review the [backport
guidelines](https://docs.google.com/document/d/1VyN5k91e5OVumlc0Gb9RPa3h1ewuPE705nRtioPiTvY/edit?usp=sharing)
and apply applicable `backport:*` labels.

### Identify risks

Does this PR introduce any risks? For example, consider risks like hard
to test bugs, performance regression, potential of data loss.

Describe the risk, its severity, and mitigation for each identified
risk. Invite stakeholders and evaluate how to proceed before merging.

- [ ] [See some risk
examples](https://github.com/elastic/kibana/blob/main/RISK_MATRIX.mdx)
- [ ] ...

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