Fix #7656: destroying a tunnel/bridge now first removes the tracks for cost calculation

[TrueBrain]

Fixes #7656 .

Motivation / Problem

When you build a road bridge, put tram tracks on it, and destroy the road+tram bridge, you had to pay money.
If you first removed the tram tracks and destroyed the road bridge, you gained money.

This is rather unfair, to expect a player to know the difference.

This is an effect of allowing road + tram on the same bridge, where you can build either/or on them. A player that pays attention will, without a solution like this, always notice a discrepancy. If you build a road bridge and a tram bridge and a road+tram bridge, you notice quickly enough that something is not adding up.

Description

To not over-complicate the code, I went for a simple approach: destroying a bridge is now a fixed-free + the price to remove the road/tram/rail from the bridge. In most cases this benefits the player, in some it does not.

Removing rail and tram makes you receive money, so bridges that have either of the two, are now (a lot) cheaper to destroy. Road bridges on the other hand are now slightly more expensive. I consider this an acceptable compromise.

While looking into this, I also found that destroying a bridge didn't asked you money for the end-tile (off-by-one).

Limitations

• Adding tram-tracks to a road-bridge by building a tram-bridge over a road-bridge calculates too much money. I moved this out of scope of this PR.

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 affects the save game format? (label 'savegame upgrade')
• This PR affects the GS/AI API? (label 'needs review: Script API')
  • ai_changelog.hpp, gs_changelog.hpp need updating.
  • The compatibility wrappers (compat_*.nut) need updating.
• This PR affects the NewGRF API? (label 'needs review: NewGRF')
  • PR must be added to API tracker

[James103]

Note the test results (discrepancy coming from a £360 extra cost on bridge removal):

7462: -   GetBankBalance():     1999979664
7462: +   GetBankBalance():     1999979304'
7475: -   GetBankBalance():     1999965070
7475: +   GetBankBalance():     1999964710'
7494: -   GetBankBalance():     1999959675
7494: +   GetBankBalance():     1999959315'

Also, why are there the stray apostrophes next to the number?

[TrueBrain]

Note the test results (discrepancy coming from a £360 extra cost on bridge removal):

7462: -   GetBankBalance():     1999979664
7462: +   GetBankBalance():     1999979304'
7475: -   GetBankBalance():     1999965070
7475: +   GetBankBalance():     1999964710'
7494: -   GetBankBalance():     1999959675
7494: +   GetBankBalance():     1999959315'

Also, why are there the stray apostrophes next to the number?

So I have not only the CI telling me regression failed, but also a user that tells me .. now I feel even worse for forgetting to run the regression before commit :'(