feat!: remove TCP socket support for server connections

[valoq]

Since windows 10 (1803) the OS supports unix sockets
Older systems that dont have them would fall back to tcp sockets for the lf server client connection, which then listens to localhost, where the lf server can be reached by all local users, allowing access to the actual users files and shell (in theory, I dont have windows for testing)

Fortunately this should no longer be an issue on supported windows systems, but its probably better to just remove the fallback

[CatsDeservePets]

Don't get me wrong but I don't want to merge a PR you can't test yourself.

[valoq]

I was hoping someone with Windows at hands may be willing to test it first :)

[joelim-work]

You don't need any of the socket code anymore since you are assuming that support for unix sockets exists, just set gDefaultSocketPath as how it is done in os.go.

Additionally gSocketProt is going to always just be unix now, so you can also cleanup some of the surrounding code:

• Delete gDefaultSocketProt
• Set gSocketProt to unix directly, removing the variable altogether and hardcoding unix is also probably fine
• Remove any if statements that depend on the value of gSocketProt

[joelim-work]

Looks good, thanks for the contribution.