Compose compiler functionality

[atbenmurray]

Signed-off-by: Ben Murray [email protected]

Description

This PR adds the compose compiler functionality as discussed in #4855.

The ComposeCompiler takes a list of user-defined transforms and "compiles" them for lazy compilation. This is done as an
alternative to Compose and other classes manipulating a list of transforms on a call by call basis.

The ComposeCompiler does the following:

• adds Apply instances to the appropriate locations in a list of lazy transforms (required for lazy resampling)
• adds MultiSampleTransform instances to a list of transforms for memory efficient computation (required for lazy resampling)
• adds CachedTransform instances to a list of transforms as a potential replacement mechanism for the current CachedDataset / PersistentDataset implementations

This PR doesn't change any user-facing functionality by itself as lazy resampling has not been integrated into Compose / Array and Dictionary transforms; this will follow in subsequent PR(s)

Types of changes

• Non-breaking change (fix or new feature that would not break existing functionality).
• Breaking change (fix or new feature that would cause existing functionality to change).
• New tests added to cover the changes.
• Integration tests passed locally by running ./runtests.sh -f -u --net --coverage.
• Quick tests passed locally by running ./runtests.sh --quick --unittests --disttests.
• In-line docstrings updated.
• Documentation updated, tested make html command in the docs/ folder.