doc/cat-file: make synopsis and description less confusing

doc/cat-file: make synopsis and description less confusing

The DESCRIPTION's "first form" is actually the 1st, 2nd, 3rd and 5th
form in SYNOPSIS, the "second form" is the 4th one.

Interestingly, this state of affairs was introduced in
97fe7250753b (cat-file docs: fix SYNOPSIS and "-h" output, 2021-12-28)
with the claim of "Now the two will match again." ("the two" being
DESCRIPTION and SYNOPSIS)...

The description also suffers from other correctness and clarity issues,
e.g., the "first form" paragraph discusses -p, -s and -t, but leaves out
-e, which is included in the corresponding SYNOPSIS section; the second
paragraph mentions <format>, which doesn't occur in SYNOPSIS at all, and
of the three batch options, really only describes the behavior of
--batch-check.  Also the mention of "drivers" seems an implementation
detail not adding much clarity in a short summary (and isn't expanded
upon in the rest of the man page, either).

Rather than trying to maintain one-to-one (or N-to-M) correspondence
between the DESCRIPTION and SYNOPSIS forms, creating duplication and
providing opportunities for error, shorten the former into a concise
summary describing the two general modes of operation: batch and
non-batch, leaving details to the subsequent manual sections.

While here, fix a grammar error in the description of -e and make the
following further minor improvements:

  NAME:
    shorten ("content or type and size" isn't the whole story; say
    "details" and leave the actual details to later sections)

  SYNOPSIS and --help:
    move the (--textconv | --filters) form before --batch, closer
    to the other non-batch forms

Signed-off-by: Štěpán Němec <stepnem@smrk.net>
Acked-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>