Shorten package extension names as per the Pkg docs

Since (I believe) [v1.10](https://github.com/JuliaLang/Pkg.jl/pull/4000), it is not necessary to include the parent package name in the extension package name. From the [Pkg docs](https://pkgdocs.julialang.org/v1/creating-packages/#Code-structure):

> Extensions can have arbitrary names (here ContourExt), following the format of this example is likely a good idea for extensions with a single dependency. **In Pkg output, extension names are always shown together with their parent package name.**

Start by locating the package extension declarations and compare their names with the Julia Pkg documentation linked in the issue. Shorten extension names so they no longer repeat the parent package name, then run the package's existing tests and inspect Pkg output to confirm the extensions still load and are displayed correctly.

Written by the indexing model from the issue text.