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

**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