Simplify Aer CI configuration

[mtreinish]

Summary

Currently the aer ci configuration is too onerous and prevents us from
making forward progress on development because we're constantly having
to adapt to upstream changes or system errors in CI. This has been
blocking us from potentially getting the 0.10.3 bugfix release prepared.
To improve the situation and make ci maintainable this commit makes a
few key changes to the CI system. The first is to stop installing
qiskit-terra from source. While the goal when this was done was to catch
failures from terra sooner in practice this just means we're playing
catch up constantly. Aer has a much slower patch rate compare to
qiskit-terra and in practice all doing this means is we have to fix ci
anytime someone pushes a new PR because things have bit rotted. These
breakages aren't aer's fault (at least normally) and are caused by
breaking api changes or bugs introduced during the development of terra,
which only guarantees api stability on releases. So we should treat
terra just like any other upstream dependency and install it from it's
release. Hopefully when we have proper integration testing setup in
terra the spurious failures will decrease as well. The second key change
made here is to decrease the duplication between jobs. In aer
historically we've tested every permutation of install method on
platform and python version. This was in response to early versions of
aer which were packaged incorrectly and quite poorly and had issues
installing everywhere without issue. However, this has led to a
proliferation of jobs that are testing the same thing in slightly
different ways. Additionally, because of all these jobs and limitations
in github actions around retying failed jobs things were split into 3
workflows to enable retrying subsets of jobs by platform. This however
further duplicated the jobs so that we had fast failures on each
workflow. This commit undoes this, it reduces the 3 test workflows back
into a single shared one. In that workflow we only have 1 lint job, one
set of sdist jobs, 1 json input test, and then 1 platform specific set
of unittest runs. This should hopefully decrease the wait time for CI
and also make things easier to manage moving forward.

Details and comments

[hhorii]

@mtreinish can we keep a workflow to test the latest terra as optional? I know other integration tests should cover tests with the latest qiskit-*. But, maybe, it is good to know what tests will be failed with the latest-terra in this repository.