Drop support for metadata in ironpython scripts

[Wurschdhaud]

Follow up for #3268 (comment) and #3270

To speed up loading times via the new launcher, the legacy metadata in code support should be dropped.

Steps:

• verify if this actually has a significant impact
• create an alert for the next release, if this legacy is found that it will be removed
• create a helper script, moving all legacy metadata to bundle.yaml files
• update the notion site to reflect the change
• actually remove it in the next major release
• ????
• profit.

[jmcouffin]

• document time gain
• test removal
• alert should point to helper script and 'ew not on page

Implement this for 6.3 release
Deprecate for 6.5