fix back exist_ok (#1059)

Co-authored-by: 孙圣翔²⁰₂₁ <oncwnuImVQzmrqH0o4rQfDVAePRA@git.weixin.qq.com>

expose param `exist_ok` to `_BaseClient` api `pull` (#1058)

Co-authored-by: EnderTheCoder <ggameinvader@gmail.com>

fix can't pass too long request error by update u2.jar

fix send_keys, use ime when pasteClipboard failed (#1039)

update send_keys and clear_text using 0.1.4 jar (#1036)

update send_keys and clear_text using 0.1.4 jar

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Co-authored-by: 孙圣翔²⁰₂₁ <oncwnuImVQzmrqH0o4rQfDVAePRA@git.weixin.qq.com>

Remove typo

add fallback for screenshot (#1018)

fix MockAdbProcess wait hangs bug (#1012)

use u2.jar instead of test apk (#1004)

* use u2.jar instead of test apk
* update toast api, use d.last_toast to get toast, d.clear_toast() to reset it
* add more unittests
* fix multi thread when use connect

fix DeadSystemRuntimeException not in message, close #1001