Mutex::Await/LockWhen/CondVar::Wait duplicate code, and cause additional
calls at runtime and code bloat.
Inline thin wrappers that just convert argument types and
add a single de-duped implementation for these methods.

This reduces code size, shaves off 55K from the mutex_test in release build,
and should make things marginally faster.

$ nm -nS mutex_test | egrep "(_ZN4absl5Mutex.*(Await|LockWhen))|(_ZN4absl7CondVar.*Wait)"

before:
00000000000912c0 00000000000001a8 T _ZN4absl7CondVar4WaitEPNS_5MutexE
00000000000988c0 0000000000000c36 T _ZN4absl7CondVar16WaitWithDeadlineEPNS_5MutexENS_4TimeE
000000000009a6e0 0000000000000041 T _ZN4absl5Mutex19LockWhenWithTimeoutERKNS_9ConditionENS_8DurationE
00000000000a28c0 0000000000000779 T _ZN4absl5Mutex17AwaitWithDeadlineERKNS_9ConditionENS_4TimeE
00000000000cf4e0 0000000000000011 T _ZN4absl5Mutex8LockWhenERKNS_9ConditionE
00000000000cf500 0000000000000041 T _ZN4absl5Mutex20LockWhenWithDeadlineERKNS_9ConditionENS_4TimeE
00000000000cf560 0000000000000011 T _ZN4absl5Mutex14ReaderLockWhenERKNS_9ConditionE
00000000000cf580 0000000000000041 T _ZN4absl5Mutex26ReaderLockWhenWithDeadlineERKNS_9ConditionENS_4TimeE
00000000000cf5e0 0000000000000766 T _ZN4absl5Mutex5AwaitERKNS_9ConditionE
00000000000cfd60 00000000000007b5 T _ZN4absl5Mutex16AwaitWithTimeoutERKNS_9ConditionENS_8DurationE
00000000000d0700 00000000000003cf T _ZN4absl7CondVar15WaitWithTimeoutEPNS_5MutexENS_8DurationE
000000000011c280 0000000000000041 T _ZN4absl5Mutex25ReaderLockWhenWithTimeoutERKNS_9ConditionENS_8DurationE

after:
000000000009c300 00000000000007ed T _ZN4absl7CondVar10WaitCommonEPNS_5MutexENS_24synchronization_internal13KernelTimeoutE
00000000000a03c0 00000000000006fe T _ZN4absl5Mutex11AwaitCommonERKNS_9ConditionENS_24synchronization_internal13KernelTimeoutE
000000000011ae00 0000000000000025 T _ZN4absl5Mutex14LockWhenCommonERKNS_9ConditionENS_24synchronization_internal13KernelTimeoutEb
PiperOrigin-RevId: 563729364
Change-Id: Ic6b43761f76719c01e03d43cc0e0c419e41a85c1