fix: avoid mutating resource paths in ODataRequestCount

[Louis-Stegra]

Context

Bug report: #1120

Feature scope:

CountRequestBuilder.toRequest() for OData V4 had the side effect of mutating the shared ODataResourcePath when appending $count to it. Reusing the same builder could therefore produce invalid paths such as $count/$count. This change makes ODataRequestCount copy the incoming resource path before appending extra segments, so repeated toRequest() calls remain stable and do not corrupt later execution.

That fix was inspired by a similar implementation in ODataRequestFunction

Feature scopes:

• Prevent ODataRequestCount constructors from mutating the provided ODataResourcePath
• Add a low-level regression test proving ODataRequestCount does not modify the original resource path
• Add a V4 builder-level regression test proving repeated CountRequestBuilder.toRequest() calls return the same URI

Definition of Done

• Functionality scope stated & covered
• Tests cover the scope above
• Error handling created / updated & covered by the tests above
• Documentation updated
• Release notes updated

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