EVIS: Reimplement using custom parsing code

Introduce a new implementation of ExpandVariablesInString and select
between the old and new implementations based on policy CMP0053.
Instead of cmCommandArgumentParserHelper, use a custom parser with our
own stack.  This is much faster and works well for our simple grammar.

The new behavior of CMP0053 should expand @VAR@ syntax only in certain
contexts.  All existing EVIS callers use "replaceAt == true" so
hard-code our call to the old implementation.  Update the signature to
default to "replaceAt == false" and pass "replaceAt == true" explicitly
in the call sites for configure_file and string(CONFIGURE).

Testing the configure (no generate) step with ParaView shows ~20%
performance improvement.

In terms of complete configure/generate steps, further testing with
ParaView shows a 20% performance improvement over 2.8.12.2 with Unix
Makefiles and minimal with Ninja. Ninja is less because it generate step
is the expensive part (future work will address this) by a long shot and
these changes help the configure step for the most part.

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