Fix errors due to new ref safety rules. (#169)

[RomainDGx]

Due to new ref safety rules, three differents errors appears in the NmeaTagBlockParser:

1. Error CS8347 "Cannot use a result of 'AdvanceToNextField(ref ReadOnlySpan)' in this context because it may expose variables referenced by parameter 'source' outside of their declaration scope".
   To fix this error I had added the scoped keyword in the source parameter as mentioned in Issue Update for new ref safety rules #169

2. Error CS8350 "This combination of arguments to 'NmeaTagBlockParser.ParseSentenceGrouping(ref ReadOnlySpan)' is disallowed because it may expose variables referenced by parameter 'this' outside of their declaration scope".
   To fix this error I set the method to static and remove this to call the method.

3. Error CS8352 "Cannot use variable 'remaining' in this context because it may expose referenced variables outside of their declaration scope".
   To fix this error I changed the signature of the GetEnd method. Now the source parameter is no longer in but ref. To resolve the problem of scope, the remaining parameter was removed, then the method directly update the source.
   In ParseDelimitedInt and ParseDelimitedLong I capture the original source to modify the source in GetEnd and use the original source in Utf8Parser.TryParse.

Note: Some generated code are updated when I ran the tests.

This PR fixes the issue #169.

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