Summary:
Rebased onto latest fbsource stable and verified the build passes with all tests.

Core changes:
- Introduce DatagramConfig::CongestionControlMode enum and trackingMode to control DATAGRAM-only tracking behavior
- In QuicTransportFunctions.cpp:
  - Track whether a packet contains a DATAGRAM frame
  - Allow tracking DATAGRAM-only packets when trackingMode == ConstrainedAndTracked
  - Update lossState.lastRetransmittablePacketSentTime only for retransmittable packets
- Add tests covering both Constrained and ConstrainedAndTracked modes across writable bytes scenarios

Validation:
- Built and tested both fbcode and xplat targets owning QuicTypedTransportTest.cpp; all tests passed

Commands run:
```
sl ssl
jf get D78130054
sl rebase -b b5d0ce1883d0 -d remote/fbsource/stable --tool :merge3
clang-format fbcode/quic/api/QuicTransportFunctions.cpp fbcode/quic/api/test/QuicTypedTransportTest.cpp fbcode/quic/state/TransportSettings.h xplat/quic/api/QuicTransportFunctions.cpp xplat/quic/api/test/QuicTypedTransportTest.cpp xplat/quic/state/TransportSettings.h
buck query "owner('fbcode/quic/api/test/QuicTypedTransportTest.cpp')"
buck build fbcode//quic/api/test:QuicTypedTransportTest
buck test fbcode//quic/api/test:QuicTypedTransportTest
buck query "owner('xplat/quic/api/test/QuicTypedTransportTest.cpp')"
buck build fbsource//xplat/quic/api/test:QuicTypedTransportTest
buck test fbsource//xplat/quic/api/test:QuicTypedTransportTest
sl amend --addremove
jf submit --draft
```

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Reviewed By: jbeshay

Differential Revision: D78130054

fbshipit-source-id: 733fb1d365700857dea5188f57620c75de3188f8