A few message wording/formatting cleanup patches

Hello,

While translating error messages into Japanese, I came across some
unusually formatted messages and messages that are difficult to
translate naturally into Japanese.

0001: 0001-Make-propgraph-object-descriptions-translatable.patch

getObjectDescription() currently builds the object name for
PropgraphElementRelationId incrementally with appendStringInfo(), but
that works poorly with Japanese because it effectively fixes the word
order. We probably need to construct the whole name from a single
format string instead.

0002: 0002-Use-double-quotes-in-message.patch

fe-protocol3.c has the following message containing backquotes:

> libpq_append_conn_error(conn,
> "server did not report the unsupported `_pq_.test_protocol_negotiation` parameter in its protocol negotiation message");

but that doesn't seem to match our usual style. Nearby messages use
double quotes instead.

0003: 0003-Add-missing-period-to-HINT-message.patch

In be-secure-openssl.c, the following HINT message is missing a
trailing period:

> errhint("If ssl_sni is enabled then add configuration to "%s", else "%s"",

0004: 0004-Use-singular-datachecksum-consistently-in-process-na.patch

In datachecksum_state.c, the launcher process is referred to in two
different ways: "datachecksum launcher" and "datachecksums
launcher". Considering the worker process name, I think the former is
probably the intended one, so this patch makes the naming consistent
accordingly.

That said, I can also imagine an interpretation where "datachecksums"
was chosen intentionally to refer to the checksum feature or checksum
set as a whole, so I'm not entirely sure whether this should be
considered a real issue or just a stylistic inconsistency.

Still, having both forms coexist seems somewhat error-prone in
practice, especially when typing or searching symbol names.

Regards.

--
Kyotaro Horiguchi
NTT Open Source Software Center