Still using a slightly legacy asset resolution strategy by default

[GuySartorelli]

Installer overrides the default assets file resolution strategy - this is a holdover from when this stuff was introduced in CMS 4.4

The assets module should use the optimal strategy by default, and installer should stop overriding it at all.

PRs

• https://github.com/silverstripe/silverstripe-assets/pull/542
• https://github.com/silverstripe/silverstripe-installer/pull/350

[maxime-rainville]

All merged.