Update KoreanLunisolarCalendar.cs (#17542)

Update KoreanLunisolarCalendar.cs (#17542)

* Update KoreanLunisolarCalendar.cs

Corrects two issues with the conversion table for Gregorian to Korean lunisolar dates.

Issue 1: tables use Julian month/day instead of Gregorian month/day for entries prior to 1583.
Lmon and Lday have been converted from Julian month and day to Gregorian month and day for years prior to 1583.
This also required a new value for MIN_GREGORIAN_DAY (now 19) so the minimum date now supported by this class is 19 Feb 0918 Gregorian.

Issue 2: data discrepancy in years 1586, 1587, 1648, 1659, 1692, 1753 and 1754.
Table entries for 1586, 1587, 1648, 1659, 1692, 1753 and 1754 have been corrected to match Korea Astronomy and Space Science In-
stitute (KASI) data.  Specifically:
•for years 1587, 1648, and 1754, the first day of year has been corrected
•for years 1586, 1587, 1659, 1692, 1753, and 1754, the lengths of each month have been corrected

Notes
A minor formatting change to the table has been made.  The DaysPerMonth flag has been converted to use the binary literal to ensure that changes can be made and verified easily.
See: https://github.com/dotnet/coreclr/issues/17510 for full discussion of changes.

* Update KoreanLunisolarCalendar.cs

Added comment on sources of table data.