Every time the button is pressed, the chosen led changes from '0' to '1' or from '1' to '0' respectively. Button press takes effect only after 120μs of being held (assuming `clk` is assigned to a 100MHz clock).

1.toggle_led_using_button.vhd

-- * Author: Dante Mendoza Leyva
-- * Group: 4CV13

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;
use ieee.numeric_std.all;

entity led_test is Port (
    clk:            in  std_logic;
    toggle_button:  in  std_logic;
    target_led:     out std_logic
);
end led_test;

architecture Behavioral of led_test is
    signal BUTTON_MEMORY: std_logic := '0';
    signal BUTTON_SENSIBILITY_COUNTER: integer range 0 to 120100 := 0;
    signal button_pressed: std_logic := '0';
begin
    process (clk, toggle_button)
    begin
        if (clk'event) and (clk = '1') then
            -- Every time the button is pressed, the led changes
            -- from '0' to '1' or from '1' to '0' respectively.
            if (toggle_button = '1') then -- If there is a signal comming from our button
                -- Increase sensibility counter if button_pressed has not been triggered yet
                if (button_pressed = '0') and (BUTTON_SENSIBILITY_COUNTER < 120000) then
                    BUTTON_SENSIBILITY_COUNTER <= BUTTON_SENSIBILITY_COUNTER + 1;
                end if;
                
                -- If the sensibility counter has reached the trigger limit
                -- then we set the 'button_pressed' signal to '1'
                -- and reset the counter to 0.
                if (BUTTON_SENSIBILITY_COUNTER >= 120000) then 
                    if (button_pressed = '0') then
                        BUTTON_MEMORY <= not(BUTTON_MEMORY);
                        button_pressed <= '1';
                    end if;
                end if;
            else -- If we are not receiving any signal from our button
                button_pressed <= '0';
                BUTTON_SENSIBILITY_COUNTER <= 0;
            end if;      
            target_led <= BUTTON_MEMORY;
        end if;
    end process;
end Behavioral;

constraints.xdc

set_property -dict { PACKAGE_PIN V14 IOSTANDARD LVCMOS33 } [get_ports {target_led}]
set_property -dict { PACKAGE_PIN U18 IOSTANDARD LVCMOS33 } [get_ports {toggle_button}]

set_property -dict { PACKAGE_PIN W5 IOSTANDARD LVCMOS33 } [get_ports clk]
create_clock -add -name sys_clk_pin -period 10.00 -waveform {0 5} [get_ports clk]