E2E tests: remove cargo dependency

[magnus-lindstrom]

What is introduced with this PR

This commit enables the usage of the dist/ directory, and also adds mullvad-version to it so that test-by-version.sh can operate without rust installed at all.

Also added a /dev/null redirect of a cd output so that one's able to use CDPATH while running the tests.

Why this is wanted

I would like to be able to run the e2e tests on a VM without having to compile the binaries at all, since that increases the disk size necessary for running the tests. The disk space needed drops by 20-30G this way.

How to test

1. Build all executables with scripts/container-run.sh scripts/build.sh.
2. Clone mullvadvpn-app on a system without rust installed.
3. Copy the dist folder that was created in step 1 to mullvadvpn-app/test/dist
4. Run the end to end tests using test-by-version.sh, which should not fail due to cargo missing.

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This change is 

[MarkusPettersson98]

@dlon @Serock3 What do you think?

Reviewed 3 of 3 files at r1, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved

[magnus-lindstrom]

Updated scripts to require an env var TEST_DIST_DIR to be set for dist binaries to be used, as suggested in slack by @MarkusPettersson98 . Furthermore, I thought that it would be best that in the case where the variable is defined, then all binaries in dist/ need to be there, so that you do not end up in a situation where TEST_DIST_DIR is specified, but one or more of those binaries do not exist and are silently built and used from the currently checked out commit.

[dlon]

Reviewed 2 of 2 files at r2, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved

[MarkusPettersson98]

Reviewed 2 of 2 files at r2, all commit messages.
Reviewable status: all files reviewed, 2 unresolved discussions (waiting on @magnus-lindstrom)

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test/test-by-version.sh line 17 at r2 (raw file):

    echo "  - TEST_REPORT : path to save the test results in a structured format"
    echo "Optional environment variables:"
    echo "  - TEST_DIST_DIR: Relative path to a directory with prebuilt binaries as produced by scripts/build.sh."

"Optional environment variables:" is echoed twice 😊

Code quote:

    echo "Optional environment variables:"
    echo "  - APP_VERSION: The version of the app to test (defaults to the latest stable release)"
    echo "  - APP_PACKAGE_TO_UPGRADE_FROM: The package version to upgrade from (defaults to none)"
    echo "  - TEST_FILTERS: specifies which tests to run (defaults to all)"
    echo "  - TEST_REPORT : path to save the test results in a structured format"
    echo "Optional environment variables:"
    echo "  - TEST_DIST_DIR: Relative path to a directory with prebuilt binaries as produced by scripts/build.sh."

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test/scripts/test-utils.sh line 245 at r2 (raw file):

        echo "**********************************"
        echo "* Using test-runner in dist/"

Replace dist/ with $TEST_DIST_DIR 😊

Code quote:

echo "* Using test-runner in dist/"

[MarkusPettersson98]

Reviewed 2 of 2 files at r3.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @magnus-lindstrom)

[MarkusPettersson98]

Reviewed 1 of 1 files at r4, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved

[MarkusPettersson98]

Reviewed 1 of 1 files at r5, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved