refactor: migrate resource and datasource equinix_metal_project to framework

[ocobles]

Part of #612

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 65.02836% with 185 lines in your changes are missing coverage. Please review.

Project coverage is 61.29%. Comparing base (e86dd8a) to head (30e64cc).

Files	Patch %	Lines
internal/resources/metal/project/resource.go	51.68%	68 Missing and 18 partials ⚠️
internal/resources/metal/project/datasource.go	40.74%	27 Missing and 5 partials ⚠️
internal/resources/metal/project/bgp_config.go	51.56%	27 Missing and 4 partials ⚠️
internal/planmodifiers/immutable_list.go	21.73%	16 Missing and 2 partials ⚠️
internal/resources/metal/project/models.go	83.33%	8 Missing and 3 partials ⚠️
internal/planmodifiers/immutable_int64.go	72.00%	6 Missing and 1 partial ⚠️

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Additional details and impacted files

@@             Coverage Diff             @@
##             main     #604       +/-   ##
===========================================
+ Coverage   39.04%   61.29%   +22.25%     
===========================================
  Files         114      120        +6     
  Lines       19186    19393      +207     
===========================================
+ Hits         7491    11887     +4396     
+ Misses      11489     6923     -4566     
- Partials      206      583      +377     

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[ctreatma]

The BGP update test was still failing because the project was being deleted and recreated. After some digging I found it was because organization_id was Computed with planmodifier.RequiresReplace() but was not configured with planmodifier.UseStateForUnknown(). As a result, the framework always set organization_id to unknown on plan, which marked the resource for replacement.

I updated the schema to add the missing plan modifier and updated the error message in the immutable list to match the existing test expectation: 30e64cc

[ctreatma]

Ran CI twice and observed no failures in project resource / datasource tests and a couple flakes in unrelated tests.