Previously, there were separate overrides for the options and
attributes parsing methods in the parser that were used in different
context. (Options can appear in Operator and Markup, while attributes
can appear in Expression and Markup.)

This is a refactoring that eliminates this duplicated code.
To enable it, a builder is added for the internal OptionMap type.

This is necessary for compilation on Windows, even though it's
an internal class

Co-authored-by: Elango Cheran <[email protected]>

…unctions

Several functions used to copy between vectors and arrays were written
not to take a UErrorCode, but rather to take an int argument by reference
and set it to 0 to indicate a memory allocation error. To be more
consistent with ICU style, change these functions to take a UErrorCode
argument.

Several data model classes (Reserved, Matcher and Pattern) are also
modified to add a `bogus` flag to indicate that a copy failed. Previously,
the "bogus" state was denoted by setting an internal length field to 0,
but that was wrong because a valid instance of these classes can have
length 0 and that state should be distinguished from an uninitialized
state.