support UIAutomator2

[KazuCocoa]

UiSelector().textContains(\"some value\") and UiSelector().text(\"some value\") seem broken but UiSelector().descriptionContains(\"some value\"), UiSelector().description(\"some value\"), UiSelector().resourceId(\"some value\") work fine in my environments.

So, I'd like to update some convenience methods to avoid some errors or investigate and fix https://github.com/appium/appium-uiautomator2-server or use XPath mainly for Android such as java-client.

For example, we can replace current find/s_exact to the following method. (be able to find visible elements)

• find/s_exact

find_element/s :xpath, "//*[@text='#{value}' or @content-desc='#{value}' or @resource-id='#{value}']"

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I should investigate some contains work or not. If contains works, I can replace contains method.

//#{class_name}[@visible="true" and contains(translate(@#{attr},'#{value.upcase}', '#{value}'), '#{value}')]

[KazuCocoa]

appium/appium#8349
I found an issue.