sql: addgeometrycolumn() panics when argument types don't match expectations

[knz]

Found by the RSG:

https://teamcity.cockroachdb.com/buildConfiguration/Cockroach_Nightlies_RandomSyntaxTests/2107812?showLog=2107812_13653_5028.13653

addgeometrycolumn() panics upon NULLs and various other type/value mismatches.

Example failing queries (they don't all panic for the same reasons! - see log linked above for details):

> SELECT addgeometrycolumn(e'5[\fJ_YE':::STRING, e' I.DR\x12ev-':::STRING, 127:::INT8, e'\x0eqZ':::STRING, 6398145403934288141:::INT8, NULL::bool);

>             SELECT addgeometrycolumn(e'{9\x04mnmg':::STRING, NULL::string, e'z{\x17U\x18\x14UF':::STRING, 8520410167010259393:::INT8, 'GF ;':::STRING, 7764205041022882552:::INT8) ;

>             SELECT addgeometrycolumn(e'\x126\x16\x06s':::STRING, e'Fj{\x19\x19\x13D':::STRING, NULL, '0no=i&uQ':::STRING, (SELECT NULL)::int, e'\fS@0':::STRING, (-7500098369049293782):::INT8) ;

>             SELECT addgeometrycolumn('"':::STRING, e'\x06\x03\x01\x01\x19T6f\x07':::STRING, e'89`\x1b':::STRING, 1977200249595480410:::INT8, e'{?+\n$Q':::STRING, (-3034910843779736710):::INT8, NULL) ;

>             SELECT addgeometrycolumn(e'\x04@M\x16 eE':::STRING, e'?\b\x14':::STRING, NULL, NULL, (-7099251036844177579):::INT8, true) ;

>             SELECT addgeometrycolumn(e'+;2(\x1e\x17E@#':::STRING, e'^pJb\x1f,u':::STRING, NULL::string, e'\x160\x1e':::STRING, 161857094515090885:::INT8, e'\x1fU&J\nD\tl\x1b':::STRING, (-5730490449251080638):::INT8) ;

>             SELECT addgeometrycolumn('6I':::STRING, NULL::string, NULL, e'W%\r\frA':::STRING, (-5183107820916174161):::INT8, e'8\x0e':::STRING, (SELECT NULL)::int) ;

>             SELECT addgeometrycolumn(NULL::string, '_LCc':::STRING, e'\x16S\x13*':::STRING, e'K\x02/\x1aN':::STRING, 5506395100193079333:::INT8, '':::STRING, (-1137261238327904854):::INT8, true) 

>             SELECT addgeometrycolumn(NULL, e'%\x02<\x1f[\x06u\x05':::STRING, (-5209870055390698110):::INT8, NULL::string, 7965275392428739073:::INT8) ;

cc @otan for triage.

[rytaft]

None of these queries panic anymore on master. These panics were fixed by #50992 and #51226.