sql: builtin hlc_to_timestamp doesn't handle decimals with exponents other than -10

[michae2]

Builtin function hlc_to_timestamp doesn't seem to work with decimals without ten fractional digits.

demo@127.0.0.1:26257/demoapp/defaultdb> SELECT hlc_to_timestamp(1723841815000000000);
        hlc_to_timestamp
---------------------------------
  1970-01-01 00:00:00.172384+00
(1 row)

Time: 3ms total (execution 2ms / network 2ms)

demo@127.0.0.1:26257/demoapp/defaultdb> SELECT hlc_to_timestamp(1723841815000000000.0000000000);
     hlc_to_timestamp
--------------------------
  2024-08-16 20:56:55+00
(1 row)

Time: 1ms total (execution 1ms / network 0ms)

Jira issue: CRDB-41403

[blathers-crl]

Hi @michae2, please add branch-* labels to identify which branch(es) this C-bug affects.

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