[release/10.0] Backport FormsInputDateTest fixes

[ilonatommy]

Backport of #68107 and #68115 to release/10.0

Fixes #67650.

Description

The caret has to be located over the left-most segment of the 3-segment date input, otherwise SendKeys will write to wrong segment, producing non-desired date values.

The test fails deterministically before fix and passes deterministically after the fix.

Customer Impact

None, it's just a test.

Regression?

• Yes
• No

Risk

• High
• Medium
• Low

Test fix.

Verification

• Manual (required)
• Automated

Packaging changes reviewed?

• Yes
• No
• N/A

[Copilot]

Pull request overview

Backports fixes to FormsInputDateTest on release/10.0 to make the WASM E2E tests deterministic by ensuring keyboard input starts at the left-most segment of native date/time inputs and by using a more robust clear-and-type sequence.

Changes:

• Un-quarantines the three failing WASM E2E tests and removes the now-unused Microsoft.AspNetCore.InternalTesting import.
• Introduces SetDate/ClearDate helpers to position the caret and reliably clear native inputs before sending keys.
• Fixes a typo in a comment (“Stricly” → “Strictly”).

Suppressed comments (1)

src/Components/test/E2ETest/Tests/FormsInputDateTest.cs:240

• SetDate hard-codes three Keys.ArrowLeft concatenations. This is harder to tweak/read than the existing pattern in this file that uses Enumerable.Repeat/string.Concat for repeated arrow keys.

        input.Click();
        input.SendKeys(Keys.ArrowLeft + Keys.ArrowLeft + Keys.ArrowLeft);
        input.SendKeys(keys);

[dotnet-policy-service]

Hi @ilonatommy. This PR was just approved to be included in the upcoming servicing release. Somebody from the @dotnet/aspnet-build team will get it merged when the branches are open. Until then, please make sure all the CI checks pass and the PR is reviewed.