Use the `ABSL_`-prefixed Abseil logging macros.

This is done primarily for the sake of Chromium,
which bans the unprefixed Abseil logging macros.

I mostly baked the following slices of Perl pie:

```
's,//absl/log:check",//absl/log:absl_check",'
's,//absl/log",//absl/log:absl_log",'
's,"absl/log/check.h","absl/log/absl_check.h",'
's,"absl/log/log.h","absl/log/absl_log.h",'
's,D?CHECK(_(EQ|NE|LE|LT|GE|GT))?\(,ABSL_$&,'
's,V?LOG\(,ABSL_$&,'
```

Change-Id: I65493aff42abab6865f8e2b5b769b6a651dbef3a
Reviewed-on: https://code-review.googlesource.com/c/re2/+/63092
Reviewed-by: Paul Wankadia <junyer@google.com>
Reviewed-by: Alex Chernyakhovsky <achernya@google.com>