Revert FlashStringHelper Macros

[mrengineer7777]

Description of Change

Revert to previous definition of FPSTR and F macros.

Tests scenarios

Tested on arduino-esp32 core v2.0.8 with Adafruit Huzzah32 (Feather ESP32).
Tested on Win11 computer with VSCode+PIO.

#include <Arduino.h>

const __FlashStringHelper * testfunc(void)
{
  return F("test");
}

void setup() {
  Serial.begin(115200);
  
}

void loop() {
  String s;

  // put your main code here, to run repeatedly:
  delay(1000);
  s = testfunc();
  Serial.println(s);
}

Results:

ets Jul 29 2019 12:21:46

rst:0x1 (POWERON_RESET),boot:0x13 (SPI_FAST_FLASH_BOOT)
configsip: 0, SPIWP:0xee
clk_drv:0x00,q_drv:0x00,d_drv:0x00,cs0_drv:0x00,hd_drv:0x00,wp_drv:0x00       
mode:DIO, clock div:1
load:0x3fff0030,len:1184
load:0x40078000,len:13220
ho 0 tail 12 room 4
load:0x40080400,len:3028
entry 0x400805e4
test
test
test

Related links

Closes #8108

[dok-net]

This PR is a subset of #8111, just slightly easier to digest, but as such it fails to compile this (portable) MCVE, in contrast to the complete fix as proposed in #8111:

#ifdef ESP8266
#include <ESP8266WiFi.h>
#else
#include <WiFi.h>
#endif

const char ssid[] PROGMEM = "your-ssid";

void setup()
{
    WiFi.begin(FPSTR(ssid), F("your-password"));
}

void loop()
{
}

[me-no-dev]

@dok-net in #8111 you are changing more things than necessary to achieve the object of reverting the breaking changes from your previous PR. We want to focus on that, before changing other libs.

[SuGlider]

#8147 seems to be the same, just with a different branch target for merging.
I think that @me-no-dev will merge it on both...

[SuGlider]

LGTM