To facilitate early development and testing of the new language runtime
we're introducing a temporary mechanism to opt in to using the new codepaths
based on an environment variable. This environment variable is effective
only for experiment-enabled builds of OpenTofu, and so it will be
completely ignored by official releases of OpenTofu.
This commit just deals with the "wiring" of this new mechanism, without
actually connecting it with the new language runtime yet. The goal here
is to disturb existing codepaths as little as possible to minimize both
the risk of making this change and the burden this causes for ongoing
maintenance unrelated to work on the new language runtime.
This strategy of switching at the local backend layer means that we will
have some duplicated logic in the experimental functions compared to the
non-experimental functions, which is an intentional tradeoff to allow us
to isolate what we're doing so we don't churn existing code while we're
still in this early exploration phase. In a later phase of the language
runtime project we may pivot to a different approach which switches at
a deeper point in the call stack, but for now we're keeping this broad
to give us flexibility.
Signed-off-by: Martin Atkins <mart@degeneration.co.uk>
