…lt templates

Reference: hashicorp#508

This change updates the generate command to search for multiple configuration example files using a wildcard and render all found files with the default templates (e.g. `resource*.tf` instead of just `resource.tf`). Compatibility with the existing singular `HasExample` and `ExampleFile` fields for templating is preserved, while new plural `HasExamples` and `ExampleFiles` fields were added into the template data. The testing for this feature was added by duplicating the existing "no templates" txtar, then adding second configuration example files:

```diff
4c4
< # Successful run of tfplugindocs on a Framework provider with examples but no templates or pre-exiting docs.
---
> # Successful run of tfplugindocs on a Framework provider with multiple configuration examples but no templates or pre-exiting docs.
57c57
<   configurable_attribute = "some-value"
---
>   configurable_attribute = "some-value1"
60a61,66
> ```terraform
> data "scaffolding_example" "example" {
>   configurable_attribute = "some-value2"
> }
> ```
>
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> ```terraform
> output "test" {
>   value = provider::scaffolding::example("testvalue3", "testvalue4")
> }
> ```
>
122a135,140
> }
> ```
>
> ```terraform
> output "test" {
>   value = provider::scaffolding::no-variadic("testvalue2")
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<   # example configuration here
---
>   # first example configuration here
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> ```terraform
> provider "scaffolding" {
>   # second example configuration here
> }
> ```
>
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<   configurable_attribute = "some-value"
---
>   configurable_attribute = "some-value1"
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> ```terraform
> resource "scaffolding_example" "example" {
>   configurable_attribute = "some-value2"
> }
> ```
>
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<   configurable_attribute = "some-value"
---
>   configurable_attribute = "some-value1"
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> ```terraform
> resource "scaffolding_example" "example" {
>   configurable_attribute = "some-value2"
> }
> ```
>
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<   configurable_attribute = "some-value"
---
>   configurable_attribute = "some-value1"
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> -- examples/data-sources/scaffolding_example/data-source2.tf --
> data "scaffolding_example" "example" {
>   configurable_attribute = "some-value2"
> }
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> -- examples/functions/example/function2.tf --
> output "test" {
>   value = provider::scaffolding::example("testvalue3", "testvalue4")
> }
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> -- examples/functions/no-variadic/function2.tf --
> output "test" {
>   value = provider::scaffolding::no-variadic("testvalue2")
> }
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<   # example configuration here
---
>   # first example configuration here
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> -- examples/provider/provider2.tf --
> provider "scaffolding" {
>   # second example configuration here
> }
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<   configurable_attribute = "some-value"
---
>   configurable_attribute = "some-value1"
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> -- examples/resources/scaffolding_example/resource2.tf --
> resource "scaffolding_example" "example" {
>   configurable_attribute = "some-value2"
> }
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<   configurable_attribute = "some-value"
---
>   configurable_attribute = "some-value1"
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<
---
> -- examples/ephemeral-resources/scaffolding_example/ephemeral-resource2.tf --
> resource "scaffolding_example" "example" {
>   configurable_attribute = "some-value2"
> }
```