[Merged by Bors] - feat: more lemmas on NatOrdinal

[vihdzp]

We port some more results on Ordinal into NatOrdinal.
Used within the CGT repo.

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[github-actions]

PR summary 61953c66c8

Import changes for modified files

No significant changes to the import graph

Import changes for all files

Files	Import difference

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Declarations diff

+ add_le_iff
+ instance : CharZero NatOrdinal
+ lt_add_iff
+ lt_mul_iff
+ lt_one_iff_zero
+ mul_add_lt
+ mul_le_iff
+ nmul_nadd_le
+ not_lt_zero
+ small_Icc
+ small_Ico
+ small_Iic
+ small_Iio
+ small_Ioc
+ small_Ioo
+ toNatOrdinal_natCast
+ toOrdinal_natCast
+ zero_le

You can run this locally as follows

## summary with just the declaration names:
./scripts/declarations_diff.sh <optional_commit>

## more verbose report:
./scripts/declarations_diff.sh long <optional_commit>

The doc-module for script/declarations_diff.sh contains some details about this script.

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No changes to technical debt.

You can run this locally as

./scripts/technical-debt-metrics.sh pr_summary

• The relative value is the weighted sum of the differences with weight given by the inverse of the current value of the statistic.
• The absolute value is the relative value divided by the total sum of the inverses of the current values (i.e. the weighted average of the differences).

[b-mehta]

Thanks!

bors merge

[mathlib-bors]

Pull request successfully merged into master.

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