Unignore empty values location logic 5.0.0

[SarahFrench]

I've made this PR with the intention of closing it, as I realised that this work cannot be completed until later in the plugin-framework migration project.

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Release Note Template for Downstream PRs (will be copied)

provider: empty strings provided as `location`/`region`/`zone` arguments to resources will not be ignored in favor of alternative values set on the provider

[modular-magician]

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

Diff report

Your PR generated some diffs in downstreams - here they are.

Terraform GA: Diff ( 2 files changed, 35 insertions(+), 58 deletions(-))
Terraform Beta: Diff ( 2 files changed, 35 insertions(+), 58 deletions(-))

[modular-magician]

Tests analytics

Total tests: 3035
Passed tests 2730
Skipped tests: 304
Affected tests: 1

Action taken

Found 1 affected test(s) by replaying old test recordings. Starting RECORDING based on the most recent commit. Click here to see the affected tests

TestAccVertexAIIndexEndpoint_updated

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[modular-magician]

$\textcolor{red}{\textsf{Tests failed during RECORDING mode:}}$
TestAccVertexAIIndexEndpoint_updated[Error message] [Debug log]

$\textcolor{red}{\textsf{Please fix these to complete your PR.}}$
View the build log or the debug log for each test

[SarahFrench]

Closing this PR because it would result in breaking changes for users when any datasources/resources are migrated to the plugin framework. Configs that contained empty strings in resource blocks etc would stop being valid configs