[bfrancojr]

Fixes #179.

The SBE XML converter lost fixed-length arrays that are not text. This ports protowire-go#251, following the rule in draft -01 § Fixed-Length Arrays.

Import (Convert.xmlToProto)

• A uint8 or int8 array of length N > 1 becomes bytes with (sbe.length) = N. Before, it became one narrowed uint32, so a 16-byte field was read as 1 byte and every later field in the block moved.
• An array of a wider primitive is refused with IllegalArgumentException, naming the type, the field and the message. For example: sbe: message "Record": field "uuid": type "Uuid" is an array of 2 uint64, which no proto field represents. Go uses the same text.

Export (Convert.protoToXml)

• A bytes field with (sbe.length) = N is written as primitiveType="uint8" length="N", declared once per length as bytesN. Before, it was a char array, which imports back as a string. A string stays a char array.
• A bytes field of length 1 comes back as uint32 [(sbe.encoding) = "uint8"]: the same byte in the block, but not bytes. A test pins this.

The wire bytes do not change. Only the converter's output does.

Tests (FixedArrayTest, using Go's schema and cases)

• The importer's output for the schema is checked in as arrays/arr.proto and compiled. A test checks it equals what the importer writes now.
• A codec test checks that the block layout is 45 bytes, that the uuid is at offset 12 to 28, and that the tail is in the last 4 bytes.
• XML → proto → XML → proto gives the same proto text, except the comment naming the Latin-1 encoding. Same descriptors means the same values encode to the same bytes.
• Two cases check that a wide array is refused, plus one exact-message check.
• One test pins the length-1 case.

Evidence

• ./gradlew :sbe:test: 41 tests, 0 failures. FixedArrayTest ran 9.
• With Convert.java reverted to main, 7 of the 9 fail. The two that still pass test the codec against the checked-in proto, not the converter.
• ./gradlew build with the plugin fetched at the pin (-Dorg.gradle.project.pxfJavaMeta.repo=/nonexistent, as CI does): BUILD SUCCESSFUL.