Simplifying `pyrightconfig.*.json`

[Avasam]

I'm just wondering if there's any reason to not use "typeCheckingMode": "strict" ?
The configs could be simplified to:

 [...]
 "typeCheckingMode": "strict",
 "reportPrivateUsage": "none",
 "reportIncompleteStub": "none",
 "reportMissingModuleSource": "none",
 // Incompatible overrides and property type mismatches are out of typeshed's control
 // as they are inherited from the implementation.
 "reportIncompatibleMethodOverride": "none",
 "reportIncompatibleVariableOverride": "none",
 "reportPropertyTypeMismatch": "none",
 // Overlapping overloads are often necessary in a stub, meaning pyright's check
 // (which is stricter than mypy's; see mypy issue #10143 and #10157)
 // would cause many false positives and catch few bugs.
 "reportOverlappingOverload": "none",
 // The name of the self/cls parameter is out of typeshed's control.
 "reportSelfClsParameterName": "none",

Similarly pyright.testcases.json can be simplified to:

 [...]
 "typeCheckingMode": "strict",
 "reportPropertyTypeMismatch": "error",
 "reportUnnecessaryTypeIgnoreComment": "error",
 "reportMissingModuleSource": "none",
 "reportPrivateUsage": "none",

[AlexWaygood]

I'm just wondering if there's any reason

Probably just because most of the typeshed core devs are more familiar with mypy than pyright; it hasn't broken anything being that way; and it's always been like that :)

It can probably be simplified! I'll happily review a PR.