Simplify case insensitive enum diff

[danielrbradley]

Original commit: https://github.com/pulumi/terraform-provider-azurerm/commit/5102ad61ffdce39a7fe315c975bf178f0a52c4d6

As part of the move to the 3.0 of the provider, the TF team made a
breaking change to make all enum values case sensitive

This breaks all existing Pulumi applications so we should ensure
that this is not the case for our users

This now makes up a large part of the 0005-Modify-resources.patch.

1. Do we still need these patches - does the problem of case sensitivity still apply?
2. If we still need these patches, could we apply them via gopatch so they're more robust?
3. Can we remove these patches safely with a major release

Associated helper function: suppress.CaseDifferenceV2Only

Original issue: #2052

This was split between 0004-fixup-Shared-features.patch and 0005-Modify-resources.patch.

History:

1. Originally introduced in Provider - Add the missing suppress.CaseDifference for case-insensitive string properties hashicorp/terraform-provider-azurerm#15182
2. Customised by Stack72
3. Removed in Refactor: Remove all usages of ThreePointOhBeta hashicorp/terraform-provider-azurerm#16812
4. Tweaked comment by JK

Function code:

// CaseDifferenceV2Only only suppress case difference for v2.0.
func CaseDifferenceV2Only(_, old, new string, _ *schema.ResourceData) bool {
	// FORK: Force attributes to maintain case-insensitivity to avoid breaking changes in Pulumi programs.
	return strings.EqualFold(old, new)
}