Fix inconsistent strict_optional documentation

[BHUVANSH855]

Summary

Fix the inconsistent description of strict_optional in the documentation.

Changes

• Clarify that strict_optional = true enables checking of optional types and None values.
• Explain that strict_optional = false disables that checking.
• Add links from the strict_optional and --no-strict-optional warnings to the "Optional types and the None type" documentation for additional context.

Fixes #21658

[A5rocks]

Sorry but this docs change is kind of nonsensical.

[A5rocks]

Looks good to me. @95-martin-orion what do you think?

[95-martin-orion]

Add links from the strict_optional and --no-strict-optional warnings to the "Optional types and the None type" documentation for additional context.

I don't see where these links were added, but otherwise this fixes the issue I was seeing. Thanks!

[A5rocks]

I asked them to remove the links since it didn't seem to add anything, since the sections are already describing strict-optional.

[95-martin-orion]

Fair enough. My concern (which does not need to block this PR) was that the note "--no-strict-optional is evil" provides very little information on why it is considered evil. This is fine for preventing people from using it in the first place, but not terribly helpful for users working in a codebase which already uses it.