Fix snapshot filename casing to match test method names

[glen-84]

Summary

• Three snapshot files were stored under names whose casing did not match their test methods: sharedMaxAgeAndInheritMaxAgeOnSameField, Var_is_object_with_field_a_set_to_abc_Valid, and Var_is_object_with_field_b_set_to_123_Valid. On a case-sensitive filesystem CookieCrumble does not resolve them, so it writes a second snapshot alongside the existing one instead of comparing against it.
• Renamed each file to the exact test method name. File contents are untouched (pure renames, 100% similarity).

Test plan

• Full test suite on Linux with a case-sensitive checkout: HotChocolate.Types.Tests (3509 tests) and HotChocolate.Caching.Tests (72 tests) pass on every target framework, and no snapshot files are regenerated.
• Scanned every snapshot filename segment against the identifiers declared in its test project; no further mismatches across 5971 snapshot files.

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