Most frame types have identical or very similar implementation for GetMinISize()
and GetPrefISize(), and many of them already have `IntrinsicISize()` to unify
the implementation. This patch introduces nsIFrame::IntrinsicISize() so that
derived classes only need to override one method.
`nsBlockFrame`, `ColumnSetWrapperFrame`, and `nsColumnSetFrame` are the only
three classes where their `GetMinISize()` and `GetPrefISize()` have significant
differences. Therefore, we rename `GetMinISize()` and `GetPrefISize()` to
`MinISize()` and `PrefISize`, respectively, and use them as helpers to implement
their `IntrinsicISize()`.
This patch doesn't change behavior.
Differential Revision: https://phabricator.services.mozilla.com/D217790
2969a5e0cb