pgsql: Add to_bin() and to_oct().

Add to_bin() and to_oct().

This commit introduces functions for converting numbers to their
equivalent binary and octal representations. Also, the base
conversion code for these functions and to_hex() has been moved to
a common helper function.

Co-authored-by: Eric Radman
Reviewed-by: Ian Barwick, Dag Lem, Vignesh C, Tom Lane, Peter Eisentraut, Kirk Wolak, Vik Fearing, John Naylor, Dean Rasheed
Discussion: https://postgr.es/m/Y6IyTQQ/TsD5wnsH%40vm3.eradman.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/260a1f18dae8729f99cefe4e1f759193fd6bedd0

Modified Files
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doc/src/sgml/func.sgml | 59 +++++++++++++++++++++++-
src/backend/utils/adt/varlena.c | 86 ++++++++++++++++++++++++-----------
src/include/catalog/pg_proc.dat | 12 +++++
src/test/regress/expected/strings.out | 62 ++++++++++++++++++++++++-
src/test/regress/sql/strings.sql | 15 +++++-
5 files changed, 204 insertions(+), 30 deletions(-)