Load non-sensitive data from file instead of from secrets

[michalinacienciala]

Non-sensitive data previously accessed by using secrets context is now accessed by invoking keep-network/load-env-variables action and using env context. BACKGROUND: We've been storing id of the test environment as KEEP_TEST_ETH_NETWORK_ID organization secret in GitHub's settings to allow for easy access to that value from multiple projects. But it turned out to be problematic, as GHA in some situations redacts workflow logs and actions outputs/inputs based on the values stored in secrets. So if the secret holds small numeric value, it is quite probable that at some point in time this value will be recognized as a substring of github.sha or another variable and the github.sha will be redacted with *** in place of the recognized pattern. If such redacted value is configured as input of some action, the action gets invoked by the GHA without that input, which can cause run failure or can mess up the workflow results. As a solution for this problem we decided to no longer store frequently-used, non-sensitive data such as KEEP_TEST_ETH_NETWORK_ID in GitHub's secrets, but instead store them in a file kept in keep-network/ci repository and read that data to env context in order to be able to use it when running workflows. A keep-network/load-env-variables action has been implemented to allow for loading of the variables to env context in one step. The scope of the loaded variables is limited to the job in which they were loaded. To use the variables in other job, action load-env-variables needs to be executed there as well.

[michalinacienciala]

Test configuration (references to development branch) is now removed. Here is the link to the successfully executed workflow which used that test configuration: Dapp: https://github.com/keep-network/tbtc-dapp/actions/runs/807372082