pgsql: Improve tab completion of ALTER TYPE in psql

Improve tab completion of ALTER TYPE in psql

This commit adds support for more tab completion in this command as of
"ALTER TYPE .. SET".  The completion of "RENAME VALUE" was separated
from the rest of the completions done for this command, so group
everything together.

Author: Vignesh C
Discussion: https://postgr.es/m/CALDaNm1u83jtD2wysdw9XwokEacSXEyUpELajEvOMgJTc3pQ7g@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/f6c750d31d97a66a90e3389ae6832bf99cd15f30

Modified Files
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src/bin/psql/tab-complete.c | 17 +++++++++++------
1 file changed, 11 insertions(+), 6 deletions(-)