Handle SHOPIFY_FLAG_ENVIRONMENT correctly when passed as an environment variable

[EvilGenius13]

WHY are these changes introduced?

Fixes #5594

When using the environment variable SHOPIFY_FLAG_ENVIRONMENT, you would get inconsistent behaviour. Sometimes it would read use the environment and sometimes it would ignore it and use a default or cached value.

In base-command at const environments = flags.environment ?? [] if flags.environment = myshop then environments.length would end up as 6 and skip additional processing.

WHAT is this pull request doing?

Ensure, environments ends up as an array.

How to test your changes?

Setup

• Pull down the branch
• Build the branch
• Make sure you have a shopify.theme.toml file with a few environments.
• In your terminal or bash profile, add `export SHOPIFY_FLAG_ENVIRONMENT=
• run echo $SHOPIFY_FLAG_ENVIRONMENT and make sure you see the environment output
  Testing
• Run shopify theme dev -e
• Run shopify theme dev and check if it uses
• Do the same with shopify theme list
• Change to and ensure using SHOPIFY_FLAG_ENVIRONMENT overrides a default env.

Measuring impact

How do we know this change was effective? Please choose one:

• n/a - this doesn't need measurement, e.g. a linting rule or a bug-fix
• Existing analytics will cater for this addition
• PR includes analytics changes to measure impact

Checklist

• I've considered possible cross-platform impacts (Mac, Linux, Windows)
• I've considered possible documentation changes

[github-actions]

Coverage report

St.❔	Category	Percentage	Covered / Total
🟡	Statements	78.32% (-0% 🔻)	12541/16013
🟡	Branches	72.48% (+0.02% 🔼)	6102/8419
🟡	Functions	78.44% (-0.02% 🔻)	3271/4170
🟡	Lines	78.76% (+0.01% 🔼)	11868/15068

Show files with reduced coverage 🔻

St.❔	File	Statements	Branches	Functions	Lines
🟢	... / Dev.tsx	90.59% (-2.35% 🔻)	75% (-1.79% 🔻)	86.36% (-4.55% 🔻)	92.5% (-1.25% 🔻)
🟢	... / ConcurrentOutput.tsx	98.36% (-1.64% 🔻)	92% (-4% 🔻)	100%	98.33% (-1.67% 🔻)
🟢	... / base-command.ts	87.1% (+0.28% 🔼)	86.36% (-1.14% 🔻)	82.61%	88.89% (+0.28% 🔼)

Test suite run success

2898 tests passing in 1258 suites.

Report generated by 🧪jest coverage report action from 0edf793