un-magic-number monster movecost calculation

[marilynias]

Summary

Infrastructure "un-magic-number monset movecost calculation."

Purpose of change

while working on #80555 (which I cannot reproduce with "circular distances" enabled) I found this Monstrosity:

Cataclysm-DDA/src/monmove.cpp

Lines 1619 to 1671 in 02f75a2

	int monster::calc_movecost( const tripoint &f, const tripoint &t ) const
	{
	int movecost = 0;
	map &here = get_map();
	const int source_cost = here.move_cost( f );
	const int dest_cost = here.move_cost( t );
	// Digging and flying monsters ignore terrain cost
	if( flies() || ( digging() && here.has_flag( ter_furn_flag::TFLAG_DIGGABLE, t ) ) ) {
	movecost = 100;
	// Swimming monsters move super fast in water
	} else if( swims() ) {
	if( here.has_flag( ter_furn_flag::TFLAG_SWIMMABLE, f ) ) {
	movecost += 25;
	} else {
	movecost += 50 * here.move_cost( f );
	}
	if( here.has_flag( ter_furn_flag::TFLAG_SWIMMABLE, t ) ) {
	movecost += 25;
	} else {
	movecost += 50 * here.move_cost( t );
	}
	} else if( can_submerge() ) {
	// No-breathe monsters have to walk underwater slowly
	if( here.has_flag( ter_furn_flag::TFLAG_SWIMMABLE, f ) ) {
	movecost += 250;
	} else {
	movecost += 50 * here.move_cost( f );
	}
	if( here.has_flag( ter_furn_flag::TFLAG_SWIMMABLE, t ) ) {
	movecost += 250;
	} else {
	movecost += 50 * here.move_cost( t );
	}
	movecost /= 2;
	} else if( climbs() ) {
	if( here.has_flag( ter_furn_flag::TFLAG_CLIMBABLE, f ) ) {
	movecost += 150;
	} else {
	movecost += 50 * here.move_cost( f );
	}
	if( here.has_flag( ter_furn_flag::TFLAG_CLIMBABLE, t ) ) {
	movecost += 150;
	} else {
	movecost += 50 * here.move_cost( t );
	}
	movecost /= 2;
	} else {
	movecost = ( ( 50 * source_cost ) + ( 50 * dest_cost ) ) / 2.0;
	}
	return movecost;
	}

Describe the solution

un-hardcode the monster::calc_movecost method. Make use of the existing map::combined_movecost method with arguments to be able to ignore terrain/furn/field penalties, and add the desired penalty in calc_movecost.

When ignoring terrain cost, add modifier to ensure movecost matches pre-PR values.

• Swimming (25)
• climbing (150)
• Submerged walking (originally 250, but should be handled by terrain cost)
• digging (100)
• flying (100)

Describe alternatives you've considered

Being able to separately ignore 'from' and 'to' tile. Currently it doesn't matter if only one or both tiles can be ignored.

Testing

TODO: create CI

Additional context

rl_dist actually checks for trigdist and returns it, but since it returns int there a 1-tile diagonal distance of 1.41 gets floored to 1 (probable issue of #71699). I believe it makes sense to make it return float.

[akrieger]

Please remove the IWYU submodule from the PR entirely. Not just commit a deletion but remove it from the commit history also, please.