Add MessageRecord class with Encode/Decode for the binary wire format
used in JetStream file store blocks. Uses varint-encoded lengths,
XxHash64 checksums, and a flags byte for deletion markers.
Go reference: filestore.go:6720-6724, 8180-8250, 8770-8777
13 tests covering round-trip, headers, checksum validation, corruption
detection, varint encoding, deleted flag, empty/large payloads.
Replace Deflate+XOR with IronSnappy S2 block compression and ChaCha20-Poly1305 / AES-256-GCM
AEAD encryption, matching golang/nats-server/server/filestore.go. Introduces FSV2 envelope
format alongside existing FSV1 for backward compatibility. Adds 55 new tests across
S2CodecTests, AeadEncryptorTests, and FileStoreV2Tests covering all 6 cipher×compression
permutations, tamper detection, and legacy format round-trips.
Add FrameworkReference to Microsoft.AspNetCore.App to enable Kestrel
Minimal APIs for the monitoring HTTP server. Remove the now-redundant
Microsoft.Extensions.Logging.Abstractions PackageReference (it is
included transitively via the framework reference).
Add monitoring config properties (MonitorPort, MonitorHost,
MonitorBasePath, MonitorHttpsPort) and TLS config properties (TlsCert,
TlsKey, TlsCaCert, TlsVerify, TlsHandshakeFirst, etc.) to NatsOptions.
Add TlsRequired, TlsVerify, and TlsAvailable fields to ServerInfo so
the server can advertise TLS capability in the INFO protocol message.
