Apply caching for enclave CI build

[Kailai-Wang]

Context

resolves #2140

This PR applies the caching mechanism to the enclave builds in CI after some research:

• as written in the issue, buildx GHA cache + cache mount won't work, as the cache mount won't be considered as docker layers and thus can't be persisted via buildx cache
• buildkit-cache-dance doesn't work reliably, sometimes I get empty sccache folder - see the comments in ci.yml
• cargo-chef is proven to be unsuitable for all cases

Here's an informative summary of the problem and its background, including possible solutions(workarounds): https://hackmd.io/@kobzol/S17NS71bh

In this PR, a plain copy in/out of cached data to/from docker image is performed and persisted via the official action/cache GHA. Things that are cached:

• $CARGO_HOME/registry/index
• $CARGO_HOME/registry/cache
• $CARGO_HOME/git/db
• sccache artifacts

Apart from that, this PR uses a few more techs to make it possible/more efficient:

• free up disk space
• a local-stash to store the caching only
• local registry pushing
• compressed docker export

Working example: this is a re-run with small changes to the original code:
https://github.com/litentry/litentry-parachain/actions/runs/6274181997/job/17039285320

Compilation was done within 15min, and this is the sccache stats:

There are still a few TODOs, I'll create follow-up issues.

[kziemianek]

Great work. In general it looks fine to me, just one small comment which can be resolved in separate PR if really needed..

[BillyWooo]

👍 great work.