Fixed several bugs when radio-modded explosives weren't detonating

[Night-Pryanik]

Summary

SUMMARY: Bugfixes "Fixed several bugs when radio-modded explosives weren't detonating."

Purpose of change

Closes #20384 - Detonating bombs in RC cars is bugged.

Describe the solution

• Removed trigger_rc_items and trigger_radio_item functions as my testing show that they effectively duplicated the sendRadioSignal functionality and because they ain't used anywhere else in the code, they are redundant.
• Added a check for radio-containers (RC cars) with embedded radio-modded explosives in player's possession. The game will forbid detonating these containers in this case.
• Replaced scanning for items in player inventory with checking for 30-tile radius around player.
  First, this fixed a bug when radio-modded explosive didn't detonate if it was placed in a RC car and then was taken back and you click on a button on RC control.
  Second, this means limited range of radio controls (30 tiles) instead of previous unlimited range.
  Third, this means scanning all items in huge radius. This might possibly negatively affect performance, but it should only happen on activating radio controls, which is a rare case AFAIK, so IMO it's not a big issue.
• Other small fixes here and there (typos fixing, period in the end of the sentence, int-to-string conversion simplification etc)

Describe alternatives you've considered

None.

Testing

A LOT.
Tested by wielding radio-modded grenade and RC car with this grenade and activating radio controls.
Tested by placing and throwing grenade and RC car and activating controls.
Tested by placing grenade in RC car and then taking it back and activating controls.
Tested by linking grenade to red signal and activating green signal.
Tested by linking both grenade and RC car with grenade to the same signal and activating it.
As far as I can tell, all is working as it should.

Additional context

None.