Fix: server's client is shown incorrectly in some cases

[rubidium42]

Motivation / Problem

Create a save that has companies, but no company with id 0. Start a server from the GUI and load this save. The client will now play as company with id 1, but be shown as an invalid company in the client list. In other words ci->client_playas is incorrect.

Tangentially related to this, if you load a scenario or save, the client list won't be opened. It will open the client list for a new game and heightmap though. Similarly when loading saves the restart timer won't be reset, so if you prepare saves for your server the restart times becomes non-functional.

Furthermore, new companies in network games get their company named by the client. Except for server games, where this does not happen.

Description

• Initialise the client's ci->client_playas always as spectator.
• In OnGameStart call a new routine to properly initialise the ci->client_playas to the actually loaded company.
• Move any network related things that should happen for game starts to this new routine, like opening the client list.
• Call NetworkServerNewCompany when the company created for the server is still unnamed.

Limitations

Checklist for review

Some things are not automated, and forgotten often. This list is a reminder for the reviewers.

• The bug fix is important enough to be backported? (label: 'backport requested')
• This PR touches english.txt or translations? Check the guidelines
• This PR affects the save game format? (label 'savegame upgrade')
• This PR affects the GS/AI API? (label 'needs review: Script API')
  • ai_changelog.hpp, game_changelog.hpp need updating.
  • The compatibility wrappers (compat_*.nut) need updating.
• This PR affects the NewGRF API? (label 'needs review: NewGRF')
  • newgrf_debug_data.h may need updating.
  • PR must be added to API tracker