[Improve][TubeMQ] Simplify flush check for appendMsg in FileMsgStore

[aloyszhang]

Description

When appending msg, in FileMsgStore, we may need to flush the message(and metadata) to the disk according to the check logic https://github.com/apache/inlong/blob/master/inlong-tubemq/tubemq-server/src/main/java/org/apache/inlong/tubemq/server/broker/msgstore/disk/MsgFileStore.java?#L199~L206

But these checks are mixed which is hard to comprehend.

We should simplify it in a concise manner.

InLong Component

InLong TubeMQ

Are you willing to submit PR?

• Yes, I am willing to submit a PR!

Code of Conduct

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