Dev: replace time() with Time

[kenjis]

Replace time() with Time class.
time() is not testable.

time()
// ↓
Time::now()->getTimestamp()

See #6753 (review)

$ grep -lr 'time()' system
system/Database/MigrationRunner.php
system/Cache/Handlers/FileHandler.php
system/Cache/Handlers/PredisHandler.php
system/Cache/Handlers/WincacheHandler.php
system/Cache/Handlers/MemcachedHandler.php
system/Cache/Handlers/RedisHandler.php
system/Throttle/Throttler.php
system/Test/Fabricator.php
system/Test/TestResponse.php
system/Test/Mock/MockSession.php
system/Test/Mock/MockCache.php
system/Security/Security.php
system/Images/Handlers/ImageMagickHandler.php
system/HTTP/ResponseTrait.php
system/Files/File.php
system/Cookie/Cookie.php
system/Helpers/date_helper.php
system/ThirdParty/Kint/Parser/MicrotimePlugin.php
system/Email/Email.php
system/Debug/Toolbar/Collectors/Database.php
system/Debug/Toolbar.php
system/BaseModel.php
system/Session/Session.php
system/Session/Handlers/FileHandler.php
system/Session/Handlers/MemcachedHandler.php
system/Session/Handlers/RedisHandler.php

[ddevsr]

Updated :

$ grep -lr 'time()' system
system/Cache/Handlers/FileHandler.php
system/Database/MigrationRunner.php
system/Test/Fabricator.php
system/Test/Mock/MockCache.php
system/Test/Mock/MockSession.php
system/Test/TestResponse.php
system/ThirdParty/Kint/Parser/MicrotimePlugin.php

[kenjis]

system/ThirdParty/Kint/Parser/MicrotimePlugin.php is not our code.
We don't edit it.

[ping-yee]

Does anyone can approve the last PR #6880 ?
If this PR get merged, this issue will be solved.

[kenjis]

$ grep -lr 'time()' system
system/Cache/Handlers/PredisHandler.php
system/Throttle/Throttler.php
system/ThirdParty/Kint/Parser/MicrotimePlugin.php
system/Debug/Toolbar.php

[ddevsr]

Now completed changed

[kenjis]

Thank you! @ping-yee @ddevsr