gRPC Swift 1.21.1

SemVer Patch

• Fix a bug in protoc-gen-grpc-swift where no output would be produced Client=False,TestClient=True (#1765, patch credit to @severnt)
• Update metric serialization in logs to send integers as values (#1783, patch credit to @gliush)
• Better waiter errors with NIOTS (#1775)
• Use configured connect timeout when retries is none (#1777)
• Add scripts to fetch and generate protos and update generated files (#1784)
• Additional logging for connection pool (#1795)
• Bump version number to 1.21.1 (#1798)

Other Changes

• Fix format.sh -f printing usage (#1767, patch credit to @severnt)
• Add reflection service to .spi.yml (#1742)
• Add benchmark thresholds for nightly (#1743)
• Update @available annotations in tests to fix build for non-macOS Apple platforms (#1746)