Enable calls to find_dependency in the exported config only if we are building a static library.

[teo-tsirpanis]

#4505 replaced bundling of our dependencies' static libraries with calls to CMake's find_dependency command. We definitely need these calls when we have installed a static library, and we definitely don't need them in the release artifacts where everything is contained in a shared library.

Out of abundance of caution for potential cases where we might need these options in future scenarios, I controlled emitting these calls with TILEDB_INSTALL_FIND_DEPENDENCIES, an on-by-default option that was always enabled when building a static library. This caused disruptions in downstream projects such as SOMA because of this change in defaults.

My initial thought was to make this option off-by-default if we are not building a static library, but as it turns out we never need it enabled in such cases, because a shared library does not require linking to its dependencies when we link to it, and these dependencies are implementation details and not exposed through our public C API. Contrast this with cases like azure-storage-blobs-cpp depending on azure-storage-common-cpp at install-time, because the former's public headers depend on the latter's.

So this PR removes the TILEDB_INSTALL_FIND_DEPENDENCIES option and replaces it with TILEDB_STATIC.

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[eddelbuettel]

Thumbs up -- a build from the branch underlying this PR and its one commit does the right thing for me with SOMA.