getAllResourceProvidersFromPath doesn't work when people put a leading '/' in front of a resource scope parameter (extension scenario)

[TimLovellSmith]

Describe the bug

In PRs, people are adding suppressions because getAllResourceProvidersFromPath treats the following path declarations differently:

/{resourceUri}/providers/Microsoft.AzureStackHCI/virtualMachineInstances/default
{resourceUri}/providers/Microsoft.AzureStackHCI/virtualMachineInstances/default

with difference in leading slash.

leading to (possibly misleading) suppressions like:

directive:
  - suppress: R3020
    from:
	@@ -64,14 +64,30 @@ suppressions:
    reason: The linter is mistakenly thinking that paths for a singular resource that is always named default, like "/{resourceUri}/providers/Microsoft.AzureStackHCI/virtualMachineInstances/default," is for a collection of resources.

To Reproduce
Test with both
/{resourceUri}/providers/Microsoft.AzureStackHCI/virtualMachineInstances/default
{resourceUri}/providers/Microsoft.AzureStackHCI/virtualMachineInstances/default

Expected behavior
getAllResourceProvidersFromPath needs to see the provider name is Microsoft.AzureStackHCI but apparently its confused about that

Screenshots

Desktop (please complete the following information):
N/A

Additional context
See e.g. PR
https://github.com/Azure/azure-rest-api-specs/pull/25555/files#diff-252e313698c479b4ea491ad65d7bb1f75ccfe83aab3f773ee5bf100b1bb0a0c9
if more context on the specific API is needed