[Support] Add llvm::support::endian::writeNext (#88685)

`writeNext` overloads increase the pointer argument like `readNext`.
Code like the following
```
endian::write32<ELFT::Endianness>(p, 42);
p += 4;
endian::write32<ELFT::Endianness>(p, 43);
p += 4;
```

can be simplified to:
```
endian::writeNext<uint32_t, ELFT::Endianness>(p, 42);
endian::writeNext<uint32_t, ELFT::Endianness>(p, 43);
```