config: replace 'value_regex' with 'value_pattern'

config: replace 'value_regex' with 'value_pattern'

The 'value_regex' argument in the 'git config' builtin is poorly named,
especially related to an upcoming change that allows exact string
matches instead of ERE pattern matches.

Perform a mostly mechanical change of every instance of 'value_regex' to
'value_pattern' in the codebase. This is only critical for documentation
and error messages, but it is best to be consistent inside the codebase,
too.

For documentation, use 'value-pattern' which is better punctuation. This
affects Documentation/git-config.txt and the usage in builtin/config.c,
which was already mixed between 'value_regex' and 'value-regex'.

I gave some thought to leaving the value_regex variables inside config.c
that are regex_t pointers. However, it is probably best to keep the name
consistent with the rest of the variables.

This does not update the translations inside the po/ directory, as that
creates conflicts with ongoing work. The input strings should
automatically update through automation, and a few of the output strings
currently use "[value_regex]" directly.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>