[ISSUE #8017] fix: fix tiered store PosixFileSegment memory leak

[bxfjb]

Which Issue(s) This PR Fixes

Fixes #8017

Brief Description

• Using MappedByteBuffer in PosixFileSegment instead of FileChannel.write() or FileChannel.read() functions; avoiding FileChannel.transferFrom as it has been tested to perform poorly.

How Did You Test This Change?

See #8017