Refactor ObexTime to use java.time.Instant to prevent introducing new usages of java.util.Date.

Bug: 266796373
Bug: 271386921
Tag: #refactor
Test: atest BluetoothInstrumentationTests
(cherry picked from https://android-review.googlesource.com/q/commit:f6ce0f2f1137ea35e8501f9e00c66415955876ca)
Merged-In: I4317963a1ad324896609dd4ba98d0a893632ed23
Change-Id: I4317963a1ad324896609dd4ba98d0a893632ed23
Bug: 263323082