ramp up slang features for vscode users

[OmarTawfik]

• [ ] Ship a new extension version, including the Slang binaries.
• [ ] Ramping up flags.json settings introduced in #523 to 100% gradually.
• [ ] Observing any errors/telemetry issues in Sentry, and report/fix as-needed.
• [ ] Report any Slang issues, and integrate fixes as they are released.

cc @Xanewok as the extension was recently upgraded to the latest Slang version in #545