*: Add the -local goimports flag to the fmt Makefile target

[timflannagan]

Description

Update the "fmt" Makefile target and enable the -local goimports CLI flag. Previously, there was a TODO comment in the fmt-v2 target the mentioned the want/need to do this in the long term. This commit purges the fmt-v2 target & update the fmt target to provide the desired goimports flag. This provides a consistent module structure throughout the repository:

• Standard library dependencies
• Third party dependencies (note: over time, this will include github.com/solo-io dependencies that aren't ported over)
• Local code in the root module path

Partially related to #10444 which is tracking the root Go module name change. We'll need to also change that in the Makefile once we're closer with that stream of work.

Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works

[lgadban]

amazing

[timflannagan]

@lgadban Looks like there was merge conflicts that I resolved in the latest merge commit.