Build config option to enable builds of "leaf-node" models in jedi-bundle.

[eap]

This change introduces the new "test_strategy" flag and replaces "unittest_dependencies" with test dependencies. This allows simplified builds for some "leaf-node" packages such as models. Middle-graph packages can also select more limited builds targeting packages that are known to be affected rather than building everything.

Strategies are as follows

ALL: Used for core dependencies like oops, ioda, ufo, etc. Runs two builds and two tests in this order: unit_build -> unit_test -> integration_build -> integration_test
UNIT: Used for "leaf-node" packages like mpas-jedi and most models. Runs a single build with the specified dependencies and runs package unit test
INTEGRATION: Used for "middle-graph" packages like CRTM. Runs a single build with the specified dependencies and runs all tests for the built packages.

Examples:

• CRTM using "integration" strategy: Add jedi-ci to CRTMv3 JCSDA/CRTMv3#242
• OOPS using "all" strategy: https://github.com/JCSDA-internal/oops/pull/3013
• pyiri-jedi "unit" strategy: https://github.com/JCSDA-internal/pyiri-jedi/pull/88

Issues

Fixes: #27

Checklist

• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• I have run the unit tests before creating the PR

[ashley314]

Looks good and changes satisfy the goal of the PR. Thanks!