[NWD] Expose some EPPlus methods to improve performance.
These methods allow us to avoid using the .Cells collection in hot
codepaths, which is very useful because it can't be cached
(ExcelRange is mutable and "reading" actually mutates it). In addition,
the indexer on ExcelRange generates and parses strings, making it very
inefficient.
For the common cases, we can bypass all of this and get values by row
and column.
Also, remove obsolete .NET Framework code and target .NET 8.
Change-Id: I9d3938dd17c03bb36dcf836c1d46dbda47d5ddb2
Reviewed-on: https://gnocchi-internal-review.git.corp.google.com/c/third_party/epplus/+/206801
Reviewed-by: Greg Denton <gregdenton@google.com>
7 files changed
