* Manual Xcode project fixups
* Remove `firebase/firestore` from paths in Firestore/core
This renames all Firestore files under `Firestore/core` to remove the
interior `firebase/firestore` directory structure. This is motivated by
build failures under Windows where the filenames of intermediates were
too long.
Concretely:
* `Firebase/core/src/firebase/firestore` becomes `Firebase/core/src`
* `Firebase/core/test/firebase/firestore` becomes
`Firebase/core/test/unit`
Moving the tests into a `unit` subdirectory aligns Firestore with the
directory structure in
[AddNewPod](https://github.com/firebase/firebase-ios-sdk/blob/master/AddNewPod.md),
modified for C++ (see discussion in #3224).
Note: the output is indistinguishable from what is generated by the Objective-C library, with two exceptions:
* class names are different (due to using prefixes, e.g., `GCFS`);
* order in which map fields are outputted can be different (which I presume is to be expected).
I verified this by running integration tests and using simple diffing code to compare outputs: in the destructor of each `Message<T>` (if it's not moved-from), serialize the `Message` to bytes, create an Objective-C proto out of those bytes, convert both protos to their string form, compare the strings (ignoring minor differences in indentation, etc.). Out of 5.7K comparisons, there were just two cases of differences:
* one was in `SerializerTest.FailOnInvalidInputBytes`; since the input in question is invalid, this doesn't seem to require much attention;
* another one was due to differing floating point precision: C++ produces `1.79769e+308` while Objective-C produces `1.79769313486232e+308`. Added a TODO.
Example output:
```
2019-10-28 21:44:56.941749-0400 Firestore_Example_iOS[78883:2094242] 6.11.0 - [Firebase/Firestore][I-FST000001] WriteStream (7f903ca53d50) write request: <WriteRequest 0x70000991ef08>: {
writes {
update {
name: "projects/varconst-11-a51fd/databases/(default)/documents/test-collection/u6QizHeYjqt8Xe61kBoi"
fields {
key: "key"
value {
string_value: "value"
}
}
}
}
stream_token: "\031\020hB\002\201\364\265\265"
}
```
* Mark all dynamic and repeated fields as requiring malloc
* Remove nanopb options files
* Don't pass options-file to nanopb_cpp_generator
* Regenerate nanopb sources
No pb_callback_t fields remain
* Enable dynamic allocation support in the nanopb decoder
Gil