This function is unused.

In certain cases, the platform can be "wayland-egl", "wayland-xcomposite", and other values for which I haven't found a full list yet. Instead of matching only "wayland", we now look for "wayland" anywhere in the `QT_QPA_PLATFORM` string in a case-insensitive manner.

Acknowledgements:
`CaseInsensitiveContains`' implementation was heavily inspired by GNU's non-standard glibc `strcasestr` function, which can be found here licensed under GPLv2 or later: https://ftp.gnu.org/gnu/libc/

New rules:
`InsertNewlineAtEOF: true`
`RemoveSemicolon: true`
`RequiresClausePosition: WithPreceding`

find ./Source/ -name '*.cpp' -o -name '*.h' | xargs clang-format-19 -i

`Common::IsLower(char)` was omitted as nothing needed it.

IniFile: Migrate `Common::CaseInsensitiveLess` to StringUtil

With 12 uses of `JoinStrings` in the codebase vs 36 uses of `fmt::join`, fmtlib's range adapter for string concatenation with delimiters is clearly the preferred option.

Migrating `Common::CaseInsensitiveLess` to StringUtil.h will hopefully discourage rolling one's own solution in the future for case-insensitive associative containers when this (quite robust!) solution already exists.

`Common::CaseInsensitiveStringCompare::IsEqual` was removed in favor of using the `Common::CaseInsensitiveEquals` function.

The `a.size() != b.size()` condition in `Common::CaseInsensitiveEquals` can be removed, since `std::ranges::equal` already checks this condition (confirmed in libc++).