Fix #8297: Infrastructure counters for road tunnels, bridges, depots … (#8454)

The previous fix 887e9481ff0e70df6bf93ce15a3899a03f124c50 only worked for roads and failed to consider a multiplier used for the infrastructure totals for tunnels/bridges.
Also, depots and bus/truck stops are counted as 2 road pieces on creation but were only counted as 1 road piece on conversion because the function DiagDirToRoadBits() was used, which only ever returns single-piece road segments.

Co-authored-by: A. S <admin-git@sotai.tk>

Fix: Infrastructure total update when removing tram road stop

The wrong road owner was used when updating the tram infrastructure total.
This could result in desyncs, negative infrastructure totals, etc.

Fix #7847: Use ViewportSign coordinates for sign Kdtree coordinates (#7849)

Ensure the same coordinates are used for station/town/player signs regardless of how the landscape changes below it after the coordinates were first determined.

By keeping track of whether each ViewportSign is valid for Kdtree use (and only ever registering the viewport sign when the object is valid) a lot of code can be simplified and become more robust at the same time.

Codechange: Distance between town and airport has already just been found, so use it. (#7427)

Previously the distance was thrown away, only to be expensively recalculated again.

Fix: Incorrect display of industry production around tiles. (#7426)

Display of industry production around tiles (as shown when placing a station)
did not take account of the station catchment changes, so still showed production
from an industry even if it was not covered by a tile.

This is fixed by making a set of nearby industries that are covered, instead of
looping over all possible industries.

Fix #7372: FindStationsAroundTiles() with caching returns no result for industry tiles.

Currently this can only be triggered by NewGRF house tiles querying for cargo acceptance history
of nearby stations (var 0x64) with a tile offset, and providing an offset that happens to point
to an industry tile. This serves no useful purpose.

Feature: Industries with neutral stations (e.g. Oil Rig) only supply/accept cargo to/from their neutral station. (#7234)

This change is a controlled by a game setting, located under Environment ->
Industries which allows toggling the behaviour. It defaults to enabled.

"Company stations can serve industries with attached neutral stations"

When enabled, industries with attached neutral station (such as Oil Rigs) may
also be served by company-owned stations built nearby. This is the traditional
behaviour.

When disabled, these industries may only be served by their neutral station.
Any nearby company-owned stations won't be able to serve them, nor will the
neutral station serve anything else other than the industry.

Fix: Some code and comment typos

Found with codespell

Fix: Only possible to build station next to competitors by using CTRL+click

Fix by checking only for stations owned by the current company when
inspecting if there are multiple adjoining stations to the one being built.

When building next to 2 or more owned stations we don't know which
station should be extended. For other companies' stations that's not a
problem since our station won't merge with theirs anyway.

Calling to BuildStationPart should never have another company's station
as a parameter to attach to unless the client is malicious, so just returning
a generic error in that case.

(svn r27810) -Change: Factor out reservation-handling code in station_cmd.cpp

Code dealing with freeing and restoring track reservations is
duplicated in CmdBuildRailStation and RemoveFromRailBaseStation;
make separate functions for it. (cirdan)