Add check for inode numbers in `tiup cluster check`

Feature Request

Is your feature request related to a problem? Please describe:

Before v7.4, TiFlash may happens to inode exhausting and cause panic. Especially when users deploy TiFlash on a file system with a particularly small number of inode nodes.

https://github.com/pingcap/tiflash/issues/7595

Describe the feature you'd like:

Normally, the bytes-per-inode is 1024KiB, so we can get the expected inode number according to the total disk size. TiUP can check if the actual inode number is in the same order of magnitude as expected. If the number of inodes is too small, give a warning to the user.

Why the featue is needed:

Before v7.4, TiFlash could suffer from inode exhaust when

• Users create ten thousands of empty partition tables
• Users load lots of data of a wide table with many columns to TiFlash

Describe alternatives you've considered:

Teachability, Documentation, Adoption, Migration Strategy:

Start by locating the tiup cluster check command and its existing disk checks. Determine how to obtain total disk size and actual inode counts, then compare them using the issue's 1024KiB-per-inode expectation. Done means the command warns when the inode count is too small, with coverage for the relevant check behavior.