Added defensiveness running out of bits during parse

[theRealRobG]

Within MsbBitReader, all calls to consuming bits come with a precondition check, which causes a crash if it fails. We did have some validation within the project for making sure enough bits were left before some calls; however, it was only in select places. This change makes all calls to DataReader throwing, with a check on whether enough bits are left before allowing them to be read. This may be a dent on performance; however, it is probably worth the extra protection against application crashes.

This change is added because we found crashes in the wild due to badly formatted SCTE35 messages. These should be corrected; however, the parser should also be more defensive.

[theRealRobG]

From the test output I can see the following:
/__w/SCTE35Parser/SCTE35Parser/Tests/SCTE35ParserTests/SCTE35ParserMeasurements.swift:43: Test Case 'SCTE35ParserMeasurements.test_performance_of_many_scte35_messages' measured [Time, seconds] average: 0.005, relative standard deviation: 5.578%, values: [0.005775, 0.005625, 0.005185, 0.005238, 0.005200, 0.005216, 0.005306, 0.005277, 0.005570, 0.006080], performanceMetricID:org.swift.XCTPerformanceMetric_WallClockTime, maxPercentRelativeStandardDeviation: 10.000%, maxStandardDeviation: 0.100

Comparing against the build that introduced metrics into main branch, I see:
/__w/SCTE35Parser/SCTE35Parser/Tests/SCTE35ParserTests/SCTE35ParserMeasurements.swift:43: Test Case 'SCTE35ParserMeasurements.test_performance_of_many_scte35_messages' measured [Time, seconds] average: 0.006, relative standard deviation: 2.456%, values: [0.005982, 0.005551, 0.005536, 0.005575, 0.005534, 0.005548, 0.005564, 0.005572, 0.005511, 0.005584], performanceMetricID:org.swift.XCTPerformanceMetric_WallClockTime, maxPercentRelativeStandardDeviation: 10.000%, maxStandardDeviation: 0.100

So the performance seems no worse.