gdb: remove mi_parse::make functions

Remove the static mi_parse::make functions, and instead use the
mi_parse constructor.

This is a partial revert of the commit:

  commit fde3f93a
  Date:   Mon Mar 20 10:56:55 2023 -0600

      Introduce "static constructor" for mi_parse

which introduced the mi_parse::make functions, though after discussion
on the list the reasons for seem to have been lost[1].  Given there
are no test regressions when moving back to using the constructors, I
propose we should do that for now.

There should be no user visible changes after this commit.

[1] https://inbox.sourceware.org/gdb-patches/20230404-dap-loaded-sources-v2-5-93f229095e03@adacore.com/



Approved-By: Tom Tromey <tom@tromey.com>