[Java] Clean up usages of BaseAllocator, use BufferAllocator instead

[asfimport]

Some classes' methods use BaseAllocator or cast BufferAllocator to BaseAllocator internally instead of requiring for BufferAllocator directly, e.g. codes in AllocationManager, BufferLedger.

This can be optimized by exposing necessary methods from BufferAllocator.

Reporter: Hongze Zhang / @zhztheplayer
Assignee: Hongze Zhang / @zhztheplayer

PRs and other links:

• GitHub Pull Request #7768

_{Note: This issue was originally created as ARROW-9475. Please see the migration documentation for further details.}

[asfimport]

Micah Kornfield / @emkornfield:
Issue resolved by pull request 7768
#7768