Simplify connect_to_host logic

[KaganCanSit]

Hello,

This PR addresses code simplifications following the RAII refactoring in #5399.

Simplify connect_to_host by removing the success flag and replacing the break/return pattern with an early return on successful connection. Initialize fd with invalid_socket() instead of 0 for semantic clarity.

Additionally, the following IIFE block has no const gain (Since psk cannot later move a const object using std::move, it is copied) and can be simplified. I can add this to the branch if desired. I am not sure this change.
IIFE:

auto psk = [this]() -> std::optional<Botan::secure_vector<uint8_t>> {
    auto psk_hex = get_arg_maybe("psk");
    if(psk_hex) {
        return Botan::hex_decode_locked(psk_hex.value());
    } else {
        return {};
    }
}();

Change:

std::optional<Botan::secure_vector<uint8_t>> psk{};
if(const auto psk_hex = get_arg_maybe("psk")) {
    psk = Botan::hex_decode_locked(psk_hex.value());
}

Regards.

[KaganCanSit]

src/cli/tls_client.cpp:400:22: warning: Value stored to 'fd' during its initialization is never read [clang-analyzer-deadcode.DeadStores]
  400 |          socket_type fd = invalid_socket();
      |                      ^~   ~~~~~~~~~~~~~~~~
src/cli/tls_client.cpp:400:22: note: Value stored to 'fd' during its initialization is never read
  400 |          socket_type fd = invalid_socket();
      |                      ^~   ~~~~~~~~~~~~~~~~

socket_type fd = invalid_socket();
for(const addrinfo* rp = res.get(); rp != nullptr; rp = rp->ai_next) {

Clang-tidy not like this, I changing right now.

Updates:
24.05.2026 - Rebase master branch.

[coveralls]

coverage: 91.922% (+1.7%) from 90.184%
when pulling 6594524 on KaganCanSit:cleanup/tls-client-connect
into cdaa9c0 on randombit:master.