Codechange: Use std::array and std::unique_ptr for PersistentStorageArrays.

This (mostly) avoids the need for manual memory management and copying.

Change: Don't save industry history if cargo slot isn't used. (#11133)

This avoids saving history of 16 slots per industry when in many cases (NewGRF dependent) only a couple are used.

Change: Reorganise industry accept/produce arrays. (#10853)

Use a array of struct for each cargo instead of an array for each statistic.
This makes iterating for acceptance and production much simpler.
pct_transported is now calculated when needed.

Add: store headers for most savegame chunks

When a header is added, the chunk changes from CH_ARRAY type to
CH_TABLE type.

Feature: framework to make savegames self-descriptive

We won't be able to make it fully self-descriptive (looking at you
MAP-chunks), but anything else can. With this framework, we can
add headers for each chunk explaining how each chunk looks like
in detail.

They also will all be tables, making it a lot easier to read in
external tooling, and opening the way to consider a database
(like SQLite) to use as savegame format.

Lastly, with the headers in the savegame, you can freely add
fields without needing a savegame version bump; older versions
of OpenTTD will simply ignore the new field. This also means
we can remove all the SLE_CONDNULL, as they are irrelevant.

The next few commits will start using this framework.

Change: rework several CH_RIFF chunks to use CH_ARRAY instead

This adds two byte extra to those chunks, and might feel a bit
silly at first. But in later changes we will prefix CH_ARRAY with
a table header, and then this change shines.

Without this, we could still add headers to these chunks, but any
external reader wouldn't know if the CH_RIFF has them or not. This
way is much more practical, as they are now more like any other
chunk.

Codechange: Remove FOR_ALL_CHUNK_HANDLERS

Co-Authored-By: Patric Stout <truebrain@openttd.org>

Codechange: C++-ify lists for SaveLoad (#9323)

Basically, this changes "SaveLoad *" to either:
1) "SaveLoadTable" if a list of SaveLoads was meant
2) "SaveLoad &" if a single entry was meant

As added bonus, this removes SL_END / SLE_END / SLEG_END. This
also adds core/span.hpp, a "std::span"-lite.

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.

Codechange: Convert saveload numbers to enum values.

(This was mostly achieved with a few in-place regexes)

(svn r16338) -Codechange: split loading of references to two phases
In the first phase, indexes are stored. In the second phase, indexes are checked for validity and converted to pointers