chore: hide autotls under compile flag

[richard-ramos]

Adds a -d:libp2p_autotls_support flag to enable the usage of AutoTLS
As suggested by @arnetheduck, we're disabling this feature, as any additional dependency is a potential security issue.
cc: @tersec

[vladopajic]

curious if what's the better way to do this.

• could we leave types and types definitions but just remove withAutotls method in switch - then we technically disabled the feature?
• adding when defined(libp2p_autotls_support): in front of whole file removes line history (sometimes vary interesting info)

[arnetheduck]

the long-term plan is to integrate -d support with nimble feature flags using some suitable convention that has yet to be set in stone - it might be worth to experiment with newer nimble versions to understand what this could look like.

[richard-ramos]

could we leave types and types definitions but just remove withAutotls method in switch - then we technically disabled the feature?

I can try this.

it might be worth to experiment with newer nimble versions.

This sounds good, but lets do it on a separate PR whose scope is experimenting with that feature, while getting this PR merged ASAP to fix the error found by @jakubgs