`ExpandMemoryShorthands` should often use singular

**Describe the bug**
In very common contexts the abbreviations don't reflect whether the full term would correctly be singular or plural. It turns out singular is very commonly what's needed:

Those should be "mebibyte" and "kibibyte" respectively.

**Expected behavior**

If it's part of a qualifier it should be singular. (Also if the number is exactly `1` or `one`.)

Locate `ExpandMemoryShorthands` in the Rust codebase and inspect how it expands abbreviations in qualifiers and numeric contexts. Add coverage for singular forms such as “mebibyte” and “kibibyte,” including exactly `1` or `one`, and run the relevant existing tests.

Written by the indexing model from the issue text.