[PATCH] psql: Display SQLSTATE macro name in verbose error reports

Hi hackers,

Currently, when psql displays verbose error messages (\set VERBOSITY
verbose or \errverbose), it prints the 5-character SQLSTATE code. However,
developers often have to manually look up the corresponding C macro name
(e.g. ERRCODE_SYNTAX_ERROR) in the source code when writing C extensions or
dealing with internal backend code.

Attached is a small patch that improves the verbose error output in psql by
appending the symbolic SQLSTATE macro name to the end of the error report.

*Changes included in this patch:*

*1. Created a small Perl script in src/bin/psql to parse
src/backend/utils/errcodes.txt and generate a C header (sqlstate_names.h)
containing a mapping of SQLSTATE codes to their macro names.2. Hooked the
generation of this header into the psql Makefile and meson.build.3. Updated
psql's error reporting (ExecQueryAndProcessResults and
exec_command_errverbose) to perform a lookup and append the macro name if
VERBOSITY is verbose.*
Example output:
ERROR: 42601: syntax error at or near "FRO"
LINE 1: SELECT * FRO;
^
LOCATION: scanner_yyerror, scan.l:1220
SQLSTATE name: ERRCODE_SYNTAX_ERROR

I believe this will be a handy quality-of-life improvement for developers.
Looking forward to any feedback

Best regards,
Aaryan Parik