Refactor installation of C API and features supported (#8642)

* Refactor installation of C API and features supported

This commit overhauls and refactors the management of the building of
the C AP

Refactor installation of C API and features supported (#8642)

* Refactor installation of C API and features supported

This commit overhauls and refactors the management of the building of
the C API. Instead of this being script-based it's now done entirely
through CMake and CMake is the primary focus for building the C API. For
example building the C API release artifacts is now done through CMake
instead of through a shell script's `cargo build` and manually moving
artifacts.

The benefits that this brings are:

* The C API now properly hides symbols in its header files that weren't
enabled at build time. This is done through a new build-time generated
`conf.h` templated on a `conf.h.in` file in the source tree.

* The C API's project now supports enabling/disabling Cargo features to
have finer-grained support over what's included (plus auto-management
of the header file).

* Building the C API and managing it is now exclusively done through
CMake. For example invoking `doxygen` now lives in CMake, installation
lives there, etc.

The `CMakeLists.txt` file for the C API is overhauled in the process of
doing this. The build now primarily matches on the Rust target being
built rather than the host target. Additionally installation will now
install both the static and shared libraries instead of just one.
Additionally during this refactoring various bits and pieces of
Android-specific code were all removed. Management of the C toolchain
feels best left in scope of the caller (e.g. configuring `CC_*` env vars
and such) rather than here.

prtest:full

* Don't use `option` for optional strings

* Invert release build check

Also adjust some indentation

* Fix more indentation

* Remove no-longer-used variable

* Reduce duplication in feature macro

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Add Android release binaries to CI (#8601)

* Add Android release binaries to CI

This commit is inspired by #6480 and historical asks for Android
binaries. This does the bare minimum necessary to co

Add Android release binaries to CI (#8601)

* Add Android release binaries to CI

This commit is inspired by #6480 and historical asks for Android
binaries. This does the bare minimum necessary to configure C compilers
such that we can produce binaries but I'll admit that I'm no Android
developer myself so I have no idea if these are actually suitable for
use anywhere. Otherwise though this build subsumes the preexisting check
in CI that the build works for Android, so that part is removed too.

This additionally changes how the NDK is managed from before. Previously
a GitHub Action was used to download Java and the NDK and additionally
used the `cargo ndk` subcommand. That's all removed now in favor of
configuring C compilers directly with a pre-installed version of the NDK
which should help reduce the CI dependencies a bit.

* Review comments

* List Android as tier 3 target

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