[release/7.0] Rename request count to permit count on System.Threading.RateLimiting

[github-actions]

Backport of #76558 to release/7.0

/cc @BrennanConroy @AliKhalili

Customer Impact

API is inconsistent with other rate limiters (ConcurrencyLimiter) and other APIs (the options refer to permits not requests), and not what was approved during API review. This can cause confusion. And we can't change this later as it is a source breaking change.

runtime/src/libraries/System.Threading.RateLimiting/src/System/Threading/RateLimiting/SlidingWindowRateLimiterOptions.cs

Line 36 in dd6696a

public int PermitLimit { get; set; }

Testing

N/A

Risk

Code using System.Threading.RateLimiting in previews, RC1, or RC2 may fail to compile after this change if using parameter names. e.g. limiter.AttemptAcquireCore(requestCount: 3);
Fortunately, it'll be very easy to fix broken code, change requestCount to permitCount.

[dotnet-issue-labeler]

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This serves as a reminder for when your PR is modifying a ref *.cs file and adding/modifying public APIs, to please make sure the API implementation in the src *.cs file is documented with triple slash comments, so the PR reviewers can sign off that change.

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Issue Details

---

Backport of #76558 to release/7.0

/cc @BrennanConroy @AliKhalili

Customer Impact

Testing

Risk

IMPORTANT: Is this backport for a servicing release? If so and this change touches code that ships in a NuGet package, please make certain that you have added any necessary package authoring and gotten it explicitly reviewed.

Author:	github-actions[bot]
Assignees:	-
Labels:	area-System.Threading, new-api-needs-documentation
Milestone:	-

[carlossanlop]

@BrennanConroy can you please provide a code review sign-off?

[BrennanConroy]

@carlossanlop good to merge?

[carlossanlop]

CI failures:

• SynthesizeRecognizeTests.SpeechSynthesizerToSpeechRecognitionEngine - NullReferenceException #76626
• System.Net.Security.Tests unexpected process killed: https://helixre107v0xdeko0k025g8.blob.core.windows.net/dotnet-runtime-refs-pull-76623-merge-e21e3a340d8148949c/System.Net.Security.Tests/1/console.8e8193d7.log?helixlogtype=result

Signed off, approved by Tactics. Ready to merge.