Add validation for datafile_maxsize parameter

Description

When modifying the datafile_maxsize configuration parameter, the system should validate whether sufficient disk capacity is available.

Current Behavior

1. The datafile_maxsize value should be a valid and meaningful value.
2. During adaptive expansion, when expanding beyond 1G, the expansion occurs in 1G increments.
3. If the expansion reaches the configured datafile_maxsize limit, the final expansion will go up to that limit, and no further expansion is possible.
4. If the expansion hits the physical disk capacity limit before reaching the datafile_maxsize limit, it will still attempt to expand in 1G increments. If the remaining disk space is less than 1G, expansion stops. Unlike the behavior when hitting datafile_maxsize, it does not expand up to the remaining disk capacity.

Proposed Solution

Add validation logic to check for sufficient disk space when the datafile_maxsize parameter is set or modified.

No files or tests are named. Start by locating the datafile_maxsize configuration handling and adaptive expansion entry point, then trace how disk capacity and 1G expansion increments are checked. Done means setting or modifying the parameter validates available capacity and expansion handles the remaining disk space consistently with the configured limit.