pgsql: Prepare pg_dump internals for additional compression methods

Prepare pg_dump internals for additional compression methods

Commit bf9aa490db introduced a compression API in compress_io.{c,h} to
make reuse easier, and allow adding more compression algorithms.
However, pg_backup_archiver.c was not switched to this API and continued
to call the compression directly.

This commit teaches pg_backup_archiver.c about the compression API, so
that it can benefit from bf9aa490db (simpler code, easier addition of
new compression methods).

Author: Georgios Kokolatos
Reviewed-by: Michael Paquier, Rachel Heaton, Justin Pryzby, Tomas Vondra
Discussion:
https://postgr.es/m/faUNEOpts9vunEaLnmxmG-DldLSg_ql137OC3JYDmgrOMHm1RvvWY2IdBkv_CRxm5spCCb_OmKNk2T03TMm0fBEWveFF9wA1WizPuAgB7Ss%3D%40protonmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/03d02f54a64089284582cc60d94a8af09ff4e081

Modified Files
--------------
src/bin/pg_dump/compress_io.c        |  97 ++++++++++++++++++++----
src/bin/pg_dump/compress_io.h        |   4 +
src/bin/pg_dump/pg_backup_archiver.c | 138 +++++++++++++----------------------
src/bin/pg_dump/pg_backup_archiver.h |  27 +------
4 files changed, 138 insertions(+), 128 deletions(-)