Cleanup: Deprecate linear pools and child chain gauges V1

[jubeira]

Description

Linear pools should have been deprecated long ago; there is currently no plan to use them in V2 anymore.

We haven't been using old child chain gauges either: handling rewards with them is cumbersome when compared to the new child chain gauges V2, which are in use.

Skips deprecated tests, which will improve CI as well.

Type of change

• Bug fix
• New feature
• Breaking change
• Dependency changes
• Code refactor / cleanup
• Documentation or wording changes
• Other

Checklist:

• The diff is legible and has no extraneous changes
• N/A Complex code has been commented, including external interfaces
• N/A Tests are included for all code paths
• The base branch is either master, or there's a description of how to merge

Issue Resolution

N/A

[jubeira]

markdown links nailed on the first attempt 😎

[EndymionJkb]

LGTM; the new --bail option is good for this repo, too. Probably should have done this as soon as we decided not to revive them. Will definitely save some CI cycles