feat!: container-centric API with refactored underlying layer

[DDtKey]

Quite large refactoring as part of project revamp #563, and also the long-awaited refactoring #386

Now it's really simple API, e.g:

let container = GenericImage::new("redis", "7.2.4")
        .with_exposed_port(6379)
        .with_wait_for(WaitFor::message_on_stdout("Ready to accept connections"))
        .start();

I find this new API much easier to use, solves a lot of problems, and seems flexible enough to be extended.
This also works regardless of the tokio runtime flavor (multi-thread vs current-thread). And the sync API is still available, right under blocking feature (just like reqwest does).

From a maintainer's perspective this also simplifies the code, we don't have to worry about two different clients and their differences.

Docker host resolution

The host is resolved in the following order:

1. Docker host from the tc.host property in the ~/.testcontainers.properties file.
2. DOCKER_HOST environment variable.
3. Docker host from the "docker.host" property in the ~/.testcontainers.properties file.
4. Else, the default Docker socket will be returned.

Notes

• MSRV was bumped to 1.70 in order to use std::sync::OnceLock. This should NOT be a problem, tests usually executed on more recent versions (also see this ref).
• Cli client is removed, instead we provide sync (under blocking feature) and async impls based on HTTP client (bollard)
• tested with modules

Migration guide

• Sync API migration (Cli client)
  • Add blocking feature
  • Drop all usages of clients::Cli
  • Add use testcontainers::runners::SyncRunner;
  • Replace client.run(image) with image.start()
• Async API migration (Http client)
  • Remove experimental feature
  • Drop all usages of clients::Http
  • Add use testcontainers::runners::AsyncRunner;
  • Replace client.run(image) with image.start()
• ENV variable TESTCONTAINERS was renamed to TESTCONTAINERS_COMMAND and still accepts either remove (default to remove containers on drop) or keep
• ExecCommand interface was changed to builder-like:
  • use ExecCommand::new(cmd) instead of ExecCommand { ... }
  • cmd is Vec<String> now, so make sure your commands are separated
  • use any of the new methods to check the result with_container_ready_conditions & with_cmd_ready_condition

References

Closes #386
Closes #326
Closes #475
Closes #508
Closes #392
Closes #561
Closes #559
Closes #564
Closes #538
Closes #507
Closes #89
Closes #198