Migrated test towards unit-style.

This test was intended to check the internal behavior of a type and thus is more of a unit test. In this spirit, we've migrated more towards this style by stubbing an internal variable to observe the type's behavior.
State upgrade step: Add EnvUUID to charm docs.

Add an upgrade step to add the environment uuid to charm docs. Update
doc struct, call sites and tests respectively.
State, upgrade step: Add EnvUUID to Sequence doc IDs

Adds an upgrade step to add the EnvUUID to sequence doc IDs.
State upgrade step: Add EnvUUID to minUnits docs.

Add an upgrade step to add the environment uuid to minUnits docs. Update doc struct, call sites and tests.
fixed conflicts
Changed warning display for unknown config, remove tools-url on upgrade, added/modified tests. Bug 1383070.
generate-tools now merges metadata from different streams
Review fixes
Merge branch 'master' of https://github.com/juju/juju into migrate-sequences
Merge branch 'master' of https://github.com/juju/juju into migrate-sequences
Merged 1.21 upgrade steps into one list

Without this, upgrade steps really end up running in the wrong
order. Steps like the machine and instanceData env UUID migrations
really need to go first.

This change solves the immediate issue. A future change will tidy
this up so that the steps can be assigned against 1.21 final instead
of alpha1.
Merge branch 'master' of https://github.com/juju/juju into migrate-charms

Conflicts:
	upgrades/steps121_test.go
Merge pull request #973 from waigani/migrate-sequences

State, upgrade step: Add EnvUUID to Sequence doc IDs

Adds an upgrade step to add the EnvUUID to sequence doc IDs.
Merge pull request #1008 from mjs/merge-121-upgrade-steps

Merged 1.21 upgrade steps into one list

Without this, upgrade steps really end up running in the wrong order. Steps like the machine and instanceData env UUID migrations really need to go first.

This change solves the immediate issue. A future change will tidy this up so that the steps can be assigned against 1.21 final instead of alpha1.
Small tweak
Merge branch 'master' of https://github.com/juju/juju into migrate-minUnits

Conflicts:
	state/upgrades_test.go
	upgrades/steps121.go
	upgrades/steps121_test.go
Clarify comment. Bug 1383070.
Merge branch 'master' of https://github.com/juju/juju into migrate-minUnits

Conflicts:
	state/upgrades.go
	upgrades/steps121.go
Merge branch 'master' of https://github.com/juju/juju into migrate-charms

Conflicts:
	state/upgrades.go
	state/upgrades_test.go
Wireup sequences upgrade step

Add the upgrade step to add EnvUUID to sequence docs to the 121
upgrade steps.