pgsql: Remove unused typedefs

Remove unused typedefs

There were a few typedefs that were never used to define a variable or
field. This had the effect that the buildfarm's typedefs.list would
not include them, and so they would need to be re-added manually to
keep the overall pgindent result perfectly clean.

We can easily get rid of these typedefs to avoid the issue. In a few
cases, we just let the enum or struct stand on its own without a
typedef around it. In one case, an enum was abused to define flag
bits; that's better done with macro definitions.

This fixes all the remaining issues with missing entries in the
buildfarm's typedefs.list.

Reviewed-by: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Discussion: https://www.postgresql.org/message-id/1919000.1715815925@sss.pgh.pa.us

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/be5942aee7a012ce7f30bc7a6617903127f29e89

Modified Files
--------------
src/backend/commands/async.c | 6 +++---
src/backend/utils/resowner/resowner.c | 6 +++---
src/include/access/xlog.h | 4 ++--
src/include/storage/bufmgr.h | 12 ++++--------
src/tools/pgindent/typedefs.list | 4 ----
5 files changed, 12 insertions(+), 20 deletions(-)