Subzero: Fix -timing-funcs and -timing-focus flags.

Subzero: Fix -timing-funcs and -timing-focus flags.

1. Generate dummy FunctionXXX function names when either of those flags is given.

2. Remove the browser code that automatically sets F/G prefixes instead of Function/Global, since that performance tweak is no longer relevant.

3. Fix a presumably long-standing bug where -timing-focus would accumulate timings into the TLS copy of the timers, but would then try to print timing info based on the currently-empty GlobalContext copy of the timers.

BUG= none
R=kschimpf@google.com

Review URL: https://codereview.chromium.org/1855683002 .