Security comms

[eedugon]

This PR updates the certificates and security-setup information. Part of https://github.com/elastic/docs-projects/issues/346#issue-2788754652

• TOC and navigation has been changed and simplified
• Security setup methods for self-managed deployments have been organized in self-setup.md file.
• Landing pages have been updated.

Main pages to review:

• Secure your cluster or deployment
• Self-managed security setup, with childs.
• Manage TLS encryption, with childs

Still pending (not sure if doing that in this PR or in another one).

• Long tutorial: I have left it under self-managed security setup, but not sure if it's worthy at all, it's just a different tutorial covering all components. Update: doc moved back to raw content.
• Configure security in kibana (that doc has a lot of duplicated info): That's a work in progress item, I think we could remove it and just place the only needed parts somewhere else, feel free to share your thoughts. I've left the file with some comments. Update: doc updated and included in the set.

[shainaraskas]

some comments, mostly regarding the security features by deployment type stuff

[shainaraskas]

looks like https://docs-v3-preview.elastic.dev/elastic/docs-content/pull/941/deploy-manage/security/enabling-cipher-suites-for-stronger-encryption and https://docs-v3-preview.elastic.dev/elastic/docs-content/pull/941/deploy-manage/security/supported-ssltls-versions-by-jdk-version is missing applies info.

on the cipher suites page, it would be good to specify whether the cipher suites are enabled by default in other deployment types as well. there is also a floating backtick on the page that needs to be removed.

[shainaraskas]

OK comments are done now :)

all of them are either me being picky or small accuracy questions that should be easy to knock out. will checkmark this in case you're feeling excited to merge it but you should try to clean up the little style weirdness and make sure every page has applies tags.