Update TeamCity diff checker tool

[SarahFrench]

Description

This PR:

• Adds testing to the TC diff checker
• Refactors logic to add more user feedback and provide feedback about mismatches in both directions between TC config and provider code
• Changes how the tool is invoked from GHAs

Context

TeamCity diff checker has been failing for a few weeks:

Here is an example:

This error is confusing because:

• services_ga.kt only contains recaptchaenterprise, not recaptcha
• The GA provider contains only a services/recaptchaenterprise package, and there isn't a services/recaptcha.

However:

• There is a services/recaptcha in the Beta provider
• This is missing in the services_beta.kt file
  

With better user feedback this could be less confusing

[modular-magician]

Hi there, I'm the Modular magician. I've detected the following information about your changes:

Diff report

Your PR hasn't generated any diffs, but I'll let you know if a future commit does.

[modular-magician]

Hi there, I'm the Modular magician. I've detected the following information about your changes:

Diff report

Your PR hasn't generated any diffs, but I'll let you know if a future commit does.

[modular-magician]

Hi there, I'm the Modular magician. I've detected the following information about your changes:

Diff report

Your PR hasn't generated any diffs, but I'll let you know if a future commit does.

[modular-magician]

Hi there, I'm the Modular magician. I've detected the following information about your changes:

Diff report

Your PR hasn't generated any diffs, but I'll let you know if a future commit does.

[SarahFrench]

Using go list allows us to list the actual packages present in the services directory. This protects us a bit against people who name the folders differently from the package name (matching names is what is usual).

[BBBmau]

looks good! Ran the tests locally:

└─(10:05:08 on update-teamcity-diff-checker)──> go test -timeout 30s -run ^Test_ -v                                                                                                                                                                   ──(Wed,Nov27)─┘
=== RUN   Test_main_happyPaths
=== RUN   Test_main_happyPaths/something_missing_in_TeamCity_config_present_in_provider_code
=== RUN   Test_main_happyPaths/something_missing_in_provider_code_present_in_TeamCity_config
=== RUN   Test_main_happyPaths/everything_matches
--- PASS: Test_main_happyPaths (0.00s)
    --- PASS: Test_main_happyPaths/something_missing_in_TeamCity_config_present_in_provider_code (0.00s)
    --- PASS: Test_main_happyPaths/something_missing_in_provider_code_present_in_TeamCity_config (0.00s)
    --- PASS: Test_main_happyPaths/everything_matches (0.00s)
=== RUN   Test_main_unhappyPaths
=== RUN   Test_main_unhappyPaths/cannot_find_provider_service_file
=== RUN   Test_main_unhappyPaths/cannot_find_TeamCity_service_file
=== RUN   Test_main_unhappyPaths/empty_TeamCity_service_file
=== RUN   Test_main_unhappyPaths/empty_provider_service_file
--- PASS: Test_main_unhappyPaths (0.00s)
    --- PASS: Test_main_unhappyPaths/cannot_find_provider_service_file (0.00s)
    --- PASS: Test_main_unhappyPaths/cannot_find_TeamCity_service_file (0.00s)
    --- PASS: Test_main_unhappyPaths/empty_TeamCity_service_file (0.00s)
    --- PASS: Test_main_unhappyPaths/empty_provider_service_file (0.00s)
=== RUN   Test_listDifference
=== RUN   Test_listDifference/detects_when_lists_match
=== RUN   Test_listDifference/detects_when_items_from_list_A_is_missing_items_present_in_list_B_-_1_missing
=== RUN   Test_listDifference/detects_when_items_from_list_A_is_missing_items_present_in_list_B_-_2_missing
=== RUN   Test_listDifference/doesn't_detect_differences_if_list_A_is_a_superset_of_list_B
--- PASS: Test_listDifference (0.00s)
    --- PASS: Test_listDifference/detects_when_lists_match (0.00s)
    --- PASS: Test_listDifference/detects_when_items_from_list_A_is_missing_items_present_in_list_B_-_1_missing (0.00s)
    --- PASS: Test_listDifference/detects_when_items_from_list_A_is_missing_items_present_in_list_B_-_2_missing (0.00s)
    --- PASS: Test_listDifference/doesn't_detect_differences_if_list_A_is_a_superset_of_list_B (0.00s)
PASS
ok      github.com/GoogleCloudPlatform/magic-modules/tools/teamcity-diff-check  0.232s

[SarahFrench]

Thanks! I've manually tested the GHA yaml in my fork, but I'll merge this and then run the weekly check GHA on this repo to confirm all's ok

[SarahFrench]

Looks ok: https://github.com/GoogleCloudPlatform/magic-modules/actions/runs/12059681543/job/33628745318