Renamed test class to avoid conflict with the navigator page api.

[chunhtai]

Description

We introduced a new class Page in navigator page api. However, there are several classes in tests that use the same name. This pr rename those test classes to avoid future conflict.
The page api pr #50362

Related Issues

#45938

Tests

I added the following tests:

N/A

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[fluttergithubbot]

It looks like this pull request may not have tests. Please make sure to add tests before merging. If you need an exemption to this rule, contact Hixie.

Reviewers: Read the Tree Hygiene page and make sure this patch meets those guidelines before LGTMing.

[Piinks]

LGTM!