fix: configure Undertow test entity size

[Zhengcy05]

fixes #12859

Background

This PR updates the grpc-servlet Undertow tests to work with Undertow 2.2.39.Final and 2.3.21.Final.

Those releases changed Undertow's default MAX_ENTITY_SIZE to 2 MiB, which caused UndertowInteropTest.veryLargeRequest() to fail before the request reached the gRPC servlet.

Cause

UndertowInteropTest.veryLargeRequest() sends a 10 MiB unary request. The test server already configured gRPC's maxInboundMessageSize, but it did not configure Undertow's container-level entity size limit.

After the Undertow default changed, the container started rejecting the request and the client saw RST_STREAM ... CANCEL.

Changes

• Set UndertowOptions.MAX_ENTITY_SIZE explicitly in UndertowInteropTest
• Set UndertowOptions.MAX_ENTITY_SIZE explicitly in UndertowTransportTest to keep the transport test environment effectively unbounded
• Upgrade Undertow test dependencies to 2.2.39.Final and 2.3.21.Final

Verification

• ./gradlew -PskipAndroid=true -PskipCodegen=true :grpc-servlet:undertowTest --tests io.grpc.servlet.UndertowInteropTest
• ./gradlew -PskipAndroid=true -PskipCodegen=true :grpc-servlet:undertowTest --tests io.grpc.servlet.UndertowTransportTest