[Themes] - Switch the implementation of theme commands to run the TypeScript by default

[jamesmengo]

WHY are these changes introduced?

Closes https://github.com/Shopify/develop-advanced-edits/issues/316

WHAT is this pull request doing?

Replaces the dev-preview flag with an inverse stable flag so that we default to Typescript implementation

How to test your changes?

• Try running each command with and without the stable flag

Post-Release Steps

• Communications

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]

Thanks for your contribution!

Depending on what you are working on, you may want to request a review from a Shopify team:

• Themes: @shopify/advanced-edits
• UI extensions: @shopify/ui-extensions-cli
  • Checkout UI extensions: @shopify/checkout-ui-extensions-api-stewardship
• Hydrogen: @shopify/hydrogen
• Other: @shopify/app-inner-loop

[github-actions]

Coverage report

St.❔	Category	Percentage	Covered / Total
🟡	Statements	72.85% (-0.06% 🔻)	8276/11360
🟡	Branches	69.47% (-0.03% 🔻)	4041/5817
🟡	Functions	71.61% (-0.07% 🔻)	2157/3012
🟡	Lines	73.2% (-0.06% 🔻)	7829/10696

Show new covered files 🐣

St.❔	File	Statements	Branches	Functions	Lines
🔴	... / marketing_activity_extension.ts	33.33%	100%	0%	33.33%
🟢	... / marketing_activity_extension_schema.ts	100%	100%	100%	100%

Show files with reduced coverage 🔻

St.❔	File	Statements	Branches	Functions	Lines
🟢	... / common.ts	87.5% (+6.55% 🔼)	100% (+37.5% 🔼)	66.67% (-4.76% 🔻)	86.67% (+6.67% 🔼)
🟢	... / extension-to-toml.ts	87.5% (-3.41% 🔻)	87.5%	100%	100%
🟢	... / conf-store.ts	100%	83.33% (-5.86% 🔻)	100%	100%
🟡	... / constants.ts	56.25% (-2.57% 🔻)	0%	0%	60% (-2.5% 🔻)
🟢	... / validate.ts	89.74% (-0.5% 🔻)	85.71% (-0.95% 🔻)	100%	90.63% (-0.55% 🔻)
🟢	... / ConcurrentOutput.tsx	98.39% (-1.61% 🔻)	90.91% (-4.55% 🔻)	100%	98.33% (-1.67% 🔻)
🔴	... / crypto.ts	28.57% (-15.87% 🔻)	100%	28.57% (-8.93% 🔻)	28.57% (-15.87% 🔻)
🟡	... / error-handler.ts	64.89% (-0.11% 🔻)	69.23% (+0.71% 🔼)	55% (-2.14% 🔻)	65.22% (-0.09% 🔻)

Test suite run success

1860 tests passing in 846 suites.

Report generated by 🧪jest coverage report action from 2b06d21

[karreiro]

Thank you for this PR, @jamesmengo! It looks great! I've made a minor commit to update the documentation and rename the flag to --legacy ;)