chore(Combinatorics/SimpleGraph/Paths): review API

[vihdzp]

This PR does the following:

• Add grind annotations.
• Rename theorems X_isY to the more idiomatic isY_X.
• Remove many redundant namespaces.
• Golf accordingly.

---

[github-actions]

PR summary ed35afa570

Import changes for modified files

No significant changes to the import graph

Import changes for all files

Files	Import difference

---

Declarations diff

+ IsCycle.cons
+ bypass_eq_nil
+ bypass_nil
+ isCycle_cons_iff
+ isCycle_mapLe
+ isCycle_map_iff_of_injective
+ isCycle_map_of_injective
+ isPath_bypass
+ isPath_concat_iff
+ isPath_cons_iff
+ isPath_mapLe
+ isPath_map_iff_of_injective
+ isPath_map_of_injective
+ isTrail_mapLe
+ isTrail_map_iff_of_injective
+ isTrail_map_of_injective
+ map_isCycle_of_injective
- not_mem_edges_of_loop

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.

---

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).

[mathlib4-merge-conflict-bot]

This pull request has conflicts, please merge master and resolve them.