Support configuration of the static buffer size

[SkymanOne]

Feat to the use-ink/ink#1869

We should support the configuration of the static buffer size via the environment variable. However, every time the value changes ink_env crate needs to be rebuilt. We can detect the change by inspecting metadata (when use-ink/ink#1879 gets completed) and comparing to the value set in the environment. If they differ then we can run cargo clean -p ink_env && cargo build to rebuild the crate and inject the new value.

Due to limited memory allocated for each contract execution, we should also warn a user if they try to deploy a contract with a too-large buffer size (see use-ink/ink#1471 (comment))