pgsql: Expose internal function for converting int64 to numeric

Expose internal function for converting int64 to numeric

Existing callers had to take complicated detours via
DirectFunctionCall1().  This simplifies a lot of code.

Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://www.postgresql.org/message-id/flat/42b73d2d-da12-ba9f-570a-420e0cce19d9@phystech.edu

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/0aa8f764088ea0f36620ae2955fa6c54ec736c46

Modified Files
--------------
contrib/btree_gist/btree_numeric.c    |   2 +-
contrib/jsonb_plperl/jsonb_plperl.c   |   4 +-
src/backend/utils/adt/cash.c          |   7 +-
src/backend/utils/adt/dbsize.c        |  21 ++----
src/backend/utils/adt/formatting.c    |  19 ++----
src/backend/utils/adt/jsonpath_exec.c |  11 +---
src/backend/utils/adt/numeric.c       | 116 +++++++++-------------------------
src/include/utils/numeric.h           |   2 +
8 files changed, 50 insertions(+), 132 deletions(-)