use k6provider

[pablochacin]

Use k6provider to obtain a k6 binary with the dependencies required for a test.

Breaking changes

• Removes the option of a local build, as k6provider relies on a k6build service

Changes

• Removes the option to define the cache directory that stores the binaries. This directory will default to the k6provider's default
• Removes the automatic cleanup of the binaries. This functionality requires Add function for deleting a binary k6provider#39

Known issues

• Concurrent executions sharing the k6provider cache can fail Control concurrent download of binary k6provider#43

Notes to reviewers

The change set is quite large but most changes are straightforward and related to the removal of the local build option:

• Remove the option to specify the catalog URL
• Remove the option to specify the cache dir
• Remove references to the removed options in the test setup and assertions
• setup a local k6build test environment
• Do not check for binary removal after tests
• Restructure tests to share same k6build environment

[olegbespalov]

We might benefit from doing debug logs (that will be available with increased verbosity -v), like checksum, etc, here and in many other places, like imagine somebody comes to us and says it doesn't work, why? But for sure it out of the scope of this PR