Convert IntervalSet from throwing exceptions to using CHECKs with Expected error handling

Summary:
This commit converts IntervalSet to use CHECKs instead of throwing exceptions and provides safe tryInsert methods that return quic::Expected for error handling.

**Core Problem Solved:**
IntervalSet was throwing `std::invalid_argument` exceptions in two scenarios:
1. When constructing an Interval with `start > end`
2. When interval bounds exceed the maximum allowed value

This change eliminates exceptions in favor of CHECKs (for internal validation) and Expected-based error handling (for caller validation).

**Implementation Details:**

**1. IntervalSet Core Changes:**
- Replaced `throw std::invalid_argument` with `CHECK_LE` in Interval constructor
- Replaced `throw std::invalid_argument` with `CHECK_LE` in `insert(start, end)`
- Added `IntervalSetError` enum for error classification
- Added `folly::Expected` include

**2. Safe API Layer:**
- Added `tryInsert(interval)` method returning `Expected<Unit, IntervalSetError>`
- Added `tryInsert(start, end)` method with pre-validation
- Added `tryInsert(point)` method
- Added static `Interval::tryCreate()` method for safe interval construction

**3. Updated  Code:**
- **QuicWriteCodec.cpp**: Updated `fillFrameWithPacketReceiveTimestamps` to use `tryInsert`
  - Returns `QuicError` if interval validation fails
  - Maintains existing error handling patterns
- **QuicTransportFunctions.cpp**: Updated `implicitAckCryptoStream` to use `tryInsert`
  - Logs errors and continues processing other packets
  - Robust error handling for crypto stream implicit acks

Reviewed By: kvtsoy

Differential Revision: D76792362

fbshipit-source-id: 5bd7c22e69a91d60cc41c603a1f2380893f4c8a0

quic/api/QuicTransportFunctions.cpp

@@ -2147,7 +2147,15 @@ void implicitAckCryptoStream(
   implicitAck.implicit = true;
   for (const auto& op : conn.outstandings.packets) {
     if (op.packet.header.getPacketNumberSpace() == packetNumSpace) {
-      ackBlocks.insert(op.packet.header.getPacketSequenceNum());
+      auto insertResult =
+          ackBlocks.tryInsert(op.packet.header.getPacketSequenceNum());
+      if (insertResult.hasError()) {
+        LOG(ERROR) << "Failed to insert packet number into ack blocks: "
+                   << static_cast<int>(insertResult.error());
+        // Continue processing other packets - this shouldn't happen in normal
+        // operation
+        continue;
+      }
     }
   }
   if (ackBlocks.empty()) {