Invert enforcement patterns when needed
RFC7950 and yang-model-api defines pattern modifier invert-match,
which needs to be taken into account when validating incoming strings.
Mutate the pattern we expose to the codegen such that it captures
the inversion operation. This code is closely related to generated
code and string formats used therein, hence the beef of the
implementation lives in BindingMapping.
JIRA: MDSAL-314
Change-Id: Ie29745d3343f565ac6b1b5716b1ec38dd0f09bc9
Signed-off-by: Robert Varga <robert.varga@pantheon.tech>