pgsql: Switch some numeric-related functions to use soft error reportin

Switch some numeric-related functions to use soft error reporting

This commit changes some functions related to the data type numeric to
use the soft error reporting rather than a custom boolean flag (called
"have_error") that callers of these functions could rely on to bypass
the generation of ERROR reports, letting the callers do their own error
handling (timestamp, jsonpath and numeric_to_char() require them).

This results in the removal of some boilerplate code that was required
to handle both the ereport() and the "have_error" code paths bypassing
ereport(), unifying everything under the soft error reporting facility.

While on it, some duplicated error messages are removed. The function
upgraded in this commit were suffixed with "_opt_error" in their names.
They are renamed to "_safe" instead.

This change relies on d9f7f5d32f20, that has introduced the soft error
reporting infrastructure.

Author: Amul Sul <sulamul(at)gmail(dot)com>
Reviewed-by: Dean Rasheed <dean(dot)a(dot)rasheed(at)gmail(dot)com>
Discussion: https://postgr.es/m/CAAJ_b96No5h5tRuR+KhcC44YcYUCw8WAHuLoqqyyop8_k3+JDQ@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/4246a977bad6e76c4276a0d52def8a3dced154bb

Modified Files
--------------
src/backend/utils/adt/formatting.c | 6 +-
src/backend/utils/adt/jsonpath_exec.c | 62 ++++----
src/backend/utils/adt/numeric.c | 266 +++++++++++-----------------------
src/backend/utils/adt/timestamp.c | 46 +++---
src/include/utils/numeric.h | 22 ++-
5 files changed, 152 insertions(+), 250 deletions(-)