04ce1fe ci: deduplicate macOS SDK setup logic (Kittywhiskers Van Gogh)
8dd0db7 ci: fix "LC_ALL: cannot change locale (en_US.UTF-8)" in Guix container (Kittywhiskers Van Gogh)
187fe17 ci: don't stage packages in `/tmp`, reduce layers for `cppcheck` build (Kittywhiskers Van Gogh)
eef8635 ci: install `i386` packages only if host is `amd64`, merge layers (Kittywhiskers Van Gogh)
e770229 ci: purge package manager cache after each interaction (Kittywhiskers Van Gogh)
b7099ee ci: remove redundant `version` attribute, avoid `lldb` personality error (Kittywhiskers Van Gogh)
64cdc42 ci: add LLVM library path to `LD_LIBRARY_PATH` and GDB allowlist (Kittywhiskers Van Gogh)
440fd3f ci: drop distro LLVM packages, move Clang install up, set defaults (Kittywhiskers Van Gogh)

Pull request description:

  ## Additional Information

  * This pull request pulls container-specific changes from [dash#6387](#6387), [dash#6400](#6400) and [dash#6421](#6421)

  * The `HOST` check before running `setup_sdk.sh` isn't a part of the script itself as the script is written to be independent of external variables set. The caller is expected to know the conditions needed to run `setup_sdk.sh` as the script is _relatively_ agnostic to its environment.

  * The `version` attribute in the [`develop`](https://github.com/dashpay/dash/blob/a8e2316d6f9c6726a498bcae2c5c5d7354769511/contrib/containers/develop/docker-compose.yml) and [`guix`](https://github.com/dashpay/dash/blob/a8e2316d6f9c6726a498bcae2c5c5d7354769511/contrib/containers/guix/docker-compose.yml) container's `docker-compose.yml` has been dropped as the attribute has been deprecated in the compose spec ([source](https://github.com/compose-spec/compose-spec/blob/65ef9f4a5d713b405a77c45c64263f2543e65267/spec.md#version-top-level-element-obsolete)).

  * Using `LD_LIBRARY_PATH` to point to LLVM's libraries are acceptable and will not interfere with executing binaries built using the distro's packaged compiler as it will eventually search default paths and find the libraries shipped with the distro ([source](https://man7.org/linux/man-pages/man8/ld.so.8.html)).

  * Currently, running LLDB will result in a "personality set failed: Operation not permitted" error ([source](https://discourse.llvm.org/t/running-lldb-in-a-container/76801)). This is caused by its attempt at disabling ASLR for debugging.

    To work around this error, the container will now operate under relaxed restrictions (`seccomp=unconfined`). As disabling ASLR is valuable when debugging and the container is meant for developers (i.e. it isn't used for CI), we have opted to relax restrictions instead of skipping ASLR disablement.

  * As of `develop` (a8e2316), packages built by the container are stored in `/tmp`, which is inadvisable as it is the same directory used to store functional test runs and it's not too difficult to delete `/tmp`'s contents to save space in a long running [`develop`](https://github.com/dashpay/dash/blob/a8e2316d6f9c6726a498bcae2c5c5d7354769511/contrib/containers/develop/docker-compose.yml) container and then realize that both `shellcheck` and `cppcheck` are stored there and now you have to ditch the container you're working in and restart it.
    * To remedy this, packages are now built and stored in `/opt` in accordance with the FHS ([source](https://refspecs.linuxfoundation.org/FHS_3.0/fhs/ch03s13.html)). `/usr/local` was a contender but it's pre-populated, meanwhile `ls /opt` would give you a very quick picture of what's built for the container.

    * `/tmp` will not be entirely empty because [pypa/pip#10753](pypa/pip#10753) results in residual `.pem` files leaking into `/tmp` and `pyenv` stores its build log there and keeping it around has some debug value.

  ## Breaking Changes

  None expected.

  ## Checklist:

  - [x] I have performed a self-review of my own code
  - [x] I have commented my code, particularly in hard-to-understand areas
  - [x] I have added or updated relevant unit/integration/functional/e2e tests **(note: N/A)**
  - [x] I have made corresponding changes to the documentation **(note: N/A)**
  - [x] I have assigned this pull request to a milestone _(for repository code-owners and collaborators only)_

ACKs for top commit:
  UdjinM6:
    ACK 04ce1fe
  PastaPastaPasta:
    utACK 04ce1fe

Tree-SHA512: 5442ae06cb73b9bc4eec908803548195ae8fd9150422789e5f98578ad01a303b5361f9ba42fe8faee27ac91e38328b7771e4ba42b296dfa70ecbbfc7d10436b6