Use a single name for cmake find_package

[jcar87]

The PR that introduced the find_package capabilities does not follow usual CMake conventions, namely:

• the package has two different names, depending on whether shared or static was built
• the exported targets are not prefixed with a cmake namespace

this PR introduces this, such the config and targets work for the following:

• find_package(sqlite3mc) works
• target_link_libraries(xxx PRIVATE sqlite3mc::sqlite3mc_static)
• OR target_link_libraries(xxx PRIVATE sqlite3mc::sqlite3mc)

This is in line with current CMake convention (one may want to consider having the sqlite3mc::sqlite3mc be an alias for the static recipe if the shared one is not available).

By all means, feel free to disregard this PR altogether - it's just something that I noticed while reviewing conan-io/conan-center-index#27924. Lack of a namespace is relatively common (but not recommended), but the package having different names is rather unusual.

[utelle]

@jcar87 Thank you very much for providing these improvements to the CMake build.