feat: Add more lint rules

[spydon]

Description

Adds some more lint rules and fixes the issues those rules pointed out.

Checklist

• The title of my PR starts with a Conventional Commit prefix (fix:, feat:, docs: etc).
• I have read the Contributor Guide and followed the process outlined for submitting PRs.
• I have updated/added tests for ALL new/updated/fixed functionality.
• I have updated/added relevant documentation in docs and added dartdoc comments with ///.
• I have updated/added relevant examples in examples.

Breaking Change

• No, this is not a breaking change.

Related Issues

[st-pasha]

I just tried adding a single rule

linter:
  rules:
    - prefer_asserts_with_message

Into the packages/flame/analysis_options.yaml file, and sure enough it reports 28 violations of that rule. Which means that even though this PR adds the same rule, the test system somehow failed to run the proper analysis with that rule.

I haven't tried with any other rule, but I suspect there are 100 or so violations still hiding in the larger repo, and we just need to figure out why they are hiding...

[st-pasha]

Also, the prefer_asserts_with_messages is the only rule that I don't like very much. There are plenty of cases where asserts should be without messages because those messages don't add any valuable information. For example, in

assert(_parent != null, 'parent cannot be null');

the message is purely tautological and I don't see any way to actually improve it. At the same time, assert messages frequently cause the line to become longer than 80 chars, forcing a single-line assert into a more bloated 4+ lines of code.

[spydon]

I just tried adding a single rule

linter:
  rules:
    - prefer_asserts_with_message

Into the packages/flame/analysis_options.yaml file, and sure enough it reports 28 violations of that rule. Which means that even though this PR adds the same rule, the test system somehow failed to run the proper analysis with that rule.

I haven't tried with any other rule, but I suspect there are 100 or so violations still hiding in the larger repo, and we just need to figure out why they are hiding...

I think I broke it by forgetting to add rules: on the Flame pubspec, fixing now.

[spydon]

Also, the prefer_asserts_with_messages is the only rule that I don't like very much. There are plenty of cases where asserts should be without messages because those messages don't add any valuable information. For example, in

assert(_parent != null, 'parent cannot be null');

the message is purely tautological and I don't see any way to actually improve it. At the same time, assert messages frequently cause the line to become longer than 80 chars, forcing a single-line assert into a more bloated 4+ lines of code.

Removing that rule.