escape ampersand entity prefixes in pointer paths

[SABITHSAHEB]

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1. NodePointer.escape writes ' and " as '/" but leaves & alone, so a dynamic property name containing the literal text ' yields the same asPath() as a name containing a real quote: a map with the keys Key'1 and Key'1 prints /map[@name='Key'1'] for both entries.
2. Re-evaluating such a stored path with getValue, setValue or removePath then resolves to the wrong entry, so a name chosen to contain an entity sequence silently aliases a sibling entry's pointer path.
3. escape now also emits & for an ampersand that starts an ', " or & sequence, and the parser's unescape (XPath.jj and the checked-in XPathParser.java) decodes & in a single left-to-right pass, so escaped output decodes to exactly the original name.

A lone & still needs no escaping and & only decodes where it appears literally, so existing stored paths and hand-written literals like 'Tom & Jerry' parse as before; the only changed input is a literal containing the exact sequence &, which previously could not be produced by asPath() at all. The new test in DynamicPropertiesModelTest fails before the change and passes after.