No, casting a cantrip replaces all of your attacks for the turn
Each turn (by default) you have one action to use. A few examples of actions are: Attack, Cast a Spell, Dodge, and Dash (see the Actions in Combat section of the PHB for more). Taking any one of these actions means you cannot take the others (because you have already used your action for the turn).
Whenever you want to cast a spell, you take the Cast a Spell action. To attack, you take the Attack action. In your case, when you take the Attack action, your Extra Attack feature kicks in and allows you to get an additional attack. But Extra Attack only applies when you take the Attack action:
Beginning at 5th level, you can attack twice, instead of once,
whenever you take the Attack action on your turn.
Notice that this action has both "attack" and "Attack" in the description and that they refer to slightly different things. Attack (with a capital "A") refers to the Attack action; attack (with a lowercase "a") refers to any individual thing which the game considers an attack. In this case, if you take the Attack action you can then take two attacks. (This Q&A does an excellent job going further in-depth on this topic).
However, by taking the Attack action you have used your action for the turn and there is no way for you to take the Cast a Spell action which is what you would need to do in order to cast your cantrip. On the flip side, if you take the Cast a Spell action to cast your cantrip you no longer have access to your Extra Attack because it depends on you taking the Attack action.
Thus, you can either take your attacks or you can cast your cantrip but there is no way for you to replace one of the attacks granted by Extra Attack with a cantrip.
Concerning spell attacks
Some spells have, as part of their effect, spell attacks (usually the spell will tell you to make an attack roll and that is how you know it is a spell attack). However, this does not change anything about the above ruling. Even if a spell involves a spell attack, the spell is not itself an attack and it still cannot replace an attack that is part of the Attack action. The reason (as stated above) is that to cast that spell (to get the effect) you must take the Cast a Spell action regardless of whether one of its effects is a spell attack or not.
Your specific question
So fire bolt says:
Make a ranged spell attack against the target.
This means that one of the effects of the fire bolt spell is a ranged spell attack. However, that does not mean that fire bolt itself is now considered an attack. Fire bolt is still a spell and to get the effect (a ranged spell attack) you must first cast it using the Cast a Spell action.