[fix][Java Client] Fix large message sometimes cannot be split into chunks after PIP-132

[BewareMyPower]

Fixes #16195

Motivation

PIP-132 considers the
message metadata size when computing the payload chunk size and the
number of chunks. However, it could make some messages whose size is
less than maxMessageSize cannot be sent. There are two reasons:

1. The MessageMetadata will be updated after computing the payload
   chunk size, i.e. the actual metadata size would be greater.
2. OpSendMsg#getMessageHeaderAndPayloadSize doesn't exclude all bytes
   other than the metadata and payload, e.g. the 4 bytes checksum field.

For example, if the max message size is 100, send a string whose size is
60 with chunking enabled.

1. The initial metadata size is 25 so the chunk size is 75, the message
   won't be spit into chunks.
2. After serializeAndSendMessage, the metadata size becomes 32, so the
   serialized header's total size is 4 + 8 + 6 + 4 + 32 = 54, and the
   total size is 54 + 60 = 114, see headerContentSize in
   serializeCommandSendWithSize.
3. In getMessageHeaderAndPayloadSize, the returned value is computed
   by 114 - 8 - 4 = 102 > 100. The 6 bytes magic and checksum and 4
   bytes metadata length field are not included.

Modifications

• Update the message metadata before computing the chunk size.
• Compute the correct size in getMessageHeaderAndPayloadSize.

Verifying this change

Add testChunkSize to verify all sizes in range [1, maxMessageSize] can
be sent successfully when chunking is enabled.

Documentation

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[RobertIndie]

Good catch! LGTM.