Deprecate isAsciiString and replace its internal usages

[tkountis]

Motivation:
Minimize exposed CharSequences API and don't expose internal detail.

Modifications:
Deprecate isAsciiString and replace it's usages.

Result:
Cleaner API.

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Also attempted a solution with an IndexOfExtractor interface exposed directly from CharSequences and bench marked the two. The benefit was negligible (assuming that the JIT optimized for that particular case ie. CharSequence) so I chose to keep simple.

For reference:

CharSequencesBenchmark.isValidIpV4Address     thrpt    5  37734929.772 ±  935310.988  ops/s
CharSequencesBenchmark.isValidIpV4AddressNew  thrpt    5  38000362.771 ± 2153374.472  ops/s

* isValidIpV4AddressNew is with the IndexOfExtractor approach