ci: Use DOCKER_BUILDKIT for lint image #28083

Currently the lint docker/podman image has many issues:

• It relies on an EOL debian version.
• It relies on a debian version different from the one used in the CI lint task.
• It relies on the legacy docker build command, which requires the user to make cd ./ci/lint/ before the build step.
• It doesn't use the .python-version file, but a hardcoded version.

Fix all issues by using the recommended DOCKER_BUILDKIT=1 to generate the image.

Also:

• Rename /tmp/python to /python_build.
• Compress all pip install commands into one.
• Bump .python-version.

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Conflicts

Reviewers, this pull request conflicts with the following ones:

• #28076 (util: Replace std::filesystem with util/fs.h by MarcoFalke)

If you consider this pull request important, please also help to review the conflicting pull requests. Ideally, start with the one that should be merged first.

ACK https://github.com/bitcoin/bitcoin/pull/28083/commits/fa2f18ad8e386f067c2d7d5362f6b4dd84c295a0

Built the new linter container locally, verified it works as before. Change definitely simplifies things thanks to BUILDKIT.

Curiously, when I exercised the linter (by adding an unused variable to test/functional/feature_dbcrash.py), running the linter with docker run --rm -v $(pwd):/bitcoin -w /bitcoin -it bitcoin-linter didn't actually return a non-zero error code:

11:18:54 james@tacoma src/bitcoin (? ackr/28083.1.MarcoFalke.ci_use_docker_buildkit_f fa2f18a) % docker run --rm -v $(pwd):/bitcoin -w /bitcoin -it bitcoin-linter

src/crypto/ctaes in HEAD currently refers to tree 1b6c31139a71f80245c09597c343936a8e41d021
src/crypto/ctaes in HEAD was last updated in commit 8501bedd7508ac514385806e191aec21ee978891 (tree 1b6c31139a71f80245c09597c343936a8e41d021)
GOOD
src/secp256k1 in HEAD currently refers to tree 375f60db0c4a41474d0e7c2464fae64c1ba712a4
src/secp256k1 in HEAD was last updated in commit 901336eee751de088465e313dd8b500dfaf462b2 (tree 375f60db0c4a41474d0e7c2464fae64c1ba712a4)
GOOD
src/minisketch in HEAD currently refers to tree a749309e1b4edf48091edb57da6de2e8a16498a5
src/minisketch in HEAD was last updated in commit e9f1d8c27261070d209a28570ad36fe91531cdd2 (tree a749309e1b4edf48091edb57da6de2e8a16498a5)
GOOD
src/leveldb in HEAD currently refers to tree bd49d3c60051c1a8d8f030fa4ba7a29237fe7479
src/leveldb in HEAD was last updated in commit 1a463c70a368fb20316e03efac273438cf47baa3 (tree bd49d3c60051c1a8d8f030fa4ba7a29237fe7479)
GOOD
src/crc32c in HEAD currently refers to tree 5a1b5f7188bd2181e2a71d431fff282d50058e46
src/crc32c in HEAD was last updated in commit 08269e54a9a74e06c9fb72720a216d8c4d4532a2 (tree 5a1b5f7188bd2181e2a71d431fff282d50058e46)
GOOD
Args used        : 209
Args documented  : 220
Args undocumented: 0
set()
Args unknown     : 11
{'-zmqpubhashblockhwm', '-zmqpubrawtx', '-zmqpubhashtxhwm', '-zmqpubhashblock', '-zmqpubsequence', '-zmqpubrawblock', '-zmqpubsequencehwm', '-zmqpubrawtxhwm', '-zmqpubhashtx', '-includeconf', '-zmqpubrawblockhwm'}
test/functional/feature_dbcrash.py:56:9: F841 local variable 'a' is assigned to but never used
^---- failure generated from lint-python.py

11:19:44 james@tacoma src/bitcoin (?± ackr/28083.1.MarcoFalke.ci_use_docker_buildkit_f fa2f18a) % echo $?

0

Though I think this is an issue unrelated to this PR. (Returning 0 as an error code here prevents using the linter usefully within git hooks.)

Done in https://github.com/bitcoin/bitcoin/pull/28103