feat: Allow escaping $ in OQL commands by doing $$

[jasonk000]

fixes #143

Before

../org.eclipse.mat.product/target/products/org.eclipse.mat.ui.rcp.MemoryAnalyzer/macosx/cocoa/aarch64/MemoryAnalyzer.app/Contents/Eclipse/ParseHeapDump.sh \
    ~/Downloads/heapdump.hprof \
    "-command=oql \"SELECT adder.base AS base, (SELECT cell.value AS value FROM OBJECTS ${adder}.cells[0:-1] cell ) AS cells FROM java.util.concurrent.atomic.LongAdder adder \"" \
    org.eclipse.mat.api:query

After -- note carefully the escaped \$ to avoid the shell modifying the $$.

../org.eclipse.mat.product/target/products/org.eclipse.mat.ui.rcp.MemoryAnalyzer/macosx/cocoa/aarch64/MemoryAnalyzer.app/Contents/Eclipse/ParseHeapDump.sh \
    ~/Downloads/heapdump.hprof \
    "-command=oql \"SELECT adder.base AS base, (SELECT cell.value AS value FROM OBJECTS \$\${adder}.cells[0:-1] cell ) AS cells FROM java.util.concurrent.atomic.LongAdder adder \"" \
    org.eclipse.mat.api:query