feat(core): add option to use vendored openssl, closes #4470

[lucasfernog]

What kind of change does this PR introduce?

• Bugfix
• Feature
• Docs
• New Binding issue #___
• Code style update
• Refactor
• Build-related changes
• Other, please describe:

Does this PR introduce a breaking change?

• Yes, and the changes were approved in issue #___
• No

Checklist

• When resolving issues, they are referenced in the PR's title (e.g fix: remove a typo, closes #___, #___)
• A change file is added if any packages will require a version bump due to this PR per the instructions in the readme.
• I have added a convincing reason for adding this feature, if necessary

Other information

[FabianLars]

Something doesn't feel right. By disabling the default features you're basically disabling TLS altogether, right? (at least if the vendored flag is disabled? i don't know, reqwest's feature flags are so weird i can't get my head around that)

[lucasfernog]

You're right @FabianLars thanks for catching that. I was going to make the features exclusive but that doesn't work without some 1.60 features, and I forgot to remove that.