Sketch halts when using std::string and map

### Basic Infos

- [ x] This issue complies with the [issue POLICY doc](https://github.com/esp8266/Arduino/blob/master/POLICY.md).
- [ x] I have read the documentation at [readthedocs](https://arduino-esp8266.readthedocs.io/en/latest) and the issue is not addressed there.
- [x ] I have tested that the issue is present in current master branch (aka latest git).
- [ x] I have searched the issue tracker for a similar issue.
- [x ] If there is a stack dump, I have decoded it.

#### Platform

- Hardware: ESP-12
- Core Version: https://github.com/esp8266/Arduino/commit/8f71d2c04225c4b3af3fc8407ff74c2481e3904c
- Development Env: Arduino IDE
- Operating System: Windows

#### Description
I was migrating a project to esp8266-core 3.0.x when I started to hit weird execution issues (i.e. the execution suddenly halts until the watchdog triggers to restart the esp8266).

After very frustrating moments, I isolated the issue to the following MCVE, which basically it doesn't print the message `ciao` on the serial port. The same behavior can be observed on all the versions 3.0.x and on the latest git version (https://github.com/esp8266/Arduino/commit/8f71d2c04225c4b3af3fc8407ff74c2481e3904c).

After looking at possible related issues, I found #8314, but I don't know if they have a solution for that issue...

This code works with v2.7.4 and previous versions.

If you reduce the size of the hashmap by removing, for example, 15 pairs, the Serial.print() works.

```
#include
#include
#include

void setup() {
Serial.begin(115200);
Serial.println("Ciao");
}

# note that it is never used
std::unordered_map noteMapping{
{"SILENCE", 0 },
{ "B0", 31 },
{ "C1", 33 },
{ "CS1", 35 },
{ "D1", 37 },
{ "DS1", 39 },
{ "D1", 37 },
{ "DS1", 39 },
{ "E1", 41 },
{ "F1", 44 },
{ "FS1", 46 },
{ "G1", 49 },
{ "GS1", 52 },
{ "A1", 55 },
{ "AS1", 58 },
{ "B1", 62 },
{ "C2", 65 },
{ "CS2", 69 },
{ "D2", 73 },
{ "DS2", 78 },
{ "E2", 82 },
{ "F2", 87 },
{ "FS2", 93 },
{ "G2", 98 },
{ "GS2", 104 },
{ "A2", 110 },
{ "AS2", 117 },
{ "B2", 123 },
{ "C3", 131 },
{ "CS3", 139 },
{ "D3", 147 },
{ "DS3", 156 },
{ "E3", 165 },
{ "F3", 175 },
{ "FS3", 185 },
{ "G3", 196 },
{ "GS3", 208 },
{ "A3", 220 },
{ "AS3", 233 },
{ "B3", 247 },
{ "C4", 262 },
{ "CS4", 277 },
{ "D4", 294 },
{ "DS4", 311 },
{ "E4", 330 },
{ "F4", 349 },
{ "FS4", 370 },
{ "G4", 392 },
{ "GS4", 415 },
{ "A4", 440 },
{ "AS4", 466 },
{ "B4", 494 },
{ "C5", 523 },
{ "CS5", 554 },
{ "D5", 587 },
{ "DS5", 622 },
{ "E5", 659 },
{ "F5", 698 },
{ "FS5", 740 },
{ "G5", 784 },
{ "GS5", 831 },
{ "A5", 880 },
{ "AS5", 932 },
{ "B5", 988 },
{ "C6", 1047},
{ "CS6", 1109},
{ "D6", 1175},
{ "DS6", 1245},
{ "E6", 1319},
{ "F6", 1397},
{ "FS6", 1480},
{ "G6", 1568},
{ "GS6", 1661},
{ "A6", 1760},
{ "AS6", 1865},
{ "B6", 1976},
{ "C7", 2093},
{ "CS7", 2217},
{ "D7", 2349},
{ "DS7", 2489},
{ "E7", 2637},
{ "F7", 2794},
{ "FS7", 2960},
{ "G7", 3136},
{ "GS7", 3322},
{ "A7", 3520},
{ "AS7", 3729},
{ "B7", 3951},
{ "C8", 4186},
{ "CS8", 4435},
{ "D8", 4699},
{ "DS8", 4978}
};

void loop() {}
```