chore: fix import grouping, code formatting and enable goimports linter

[cornelk]

Types of changes

What sort of change does your code introduce/modify?

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.
• This change is using publicly documented (api.cloudflare.com or developers.cloudflare.com) and stable APIs.

[github-actions]

changelog detected ✅

[codecov-commenter]

Codecov Report

Merging #1121 (9e59eda) into master (e39278e) will increase coverage by 0.16%.
The diff coverage is 56.05%.

@@            Coverage Diff             @@
##           master    #1121      +/-   ##
==========================================
+ Coverage   49.94%   50.11%   +0.16%     
==========================================
  Files         115      121       +6     
  Lines       10991    11722     +731     
==========================================
+ Hits         5490     5874     +384     
- Misses       4338     4565     +227     
- Partials     1163     1283     +120     

Impacted Files	Coverage Δ
access_organization.go	64.70% <ø> (ø)
cloudflare_experimental.go	0.00% <0.00%> (ø)
convert_types.go	2.01% <ø> (+0.80%)	⬆️
custom_hostname.go	47.24% <ø> (ø)
device_posture_rule.go	61.80% <ø> (ø)
filter.go	42.96% <ø> (ø)
intelligence_asn.go	64.70% <ø> (ø)
intelligence_domain.go	64.70% <ø> (ø)
ip_list.go	33.00% <ø> (ø)
list.go	25.00% <ø> (ø)
... and 51 more

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

[github-actions]

This functionality has been released in v0.54.0.

For further feature requests or bug reports with this functionality, please create a new GitHub issue following the template. Thank you!