perf(obs): improve performance of `grid.crop`

[github-actions[bot]]

************* Module navix._version
navix/_version.py:1:0: C0114: Missing module docstring (missing-module-docstring)
************* Module navix.grid
navix/grid.py:1:0: C0114: Missing module docstring (missing-module-docstring)
navix/grid.py:34:0: C0116: Missing function or method docstring (missing-function-docstring)
navix/grid.py:38:38: W0621: Redefining name 'coordinates' from outer scope (line 34) (redefined-outer-name)
navix/grid.py:71:0: C0116: Missing function or method docstring (missing-function-docstring)
navix/grid.py:83:0: C0116: Missing function or method docstring (missing-function-docstring)
navix/grid.py:87:0: C0116: Missing function or method docstring (missing-function-docstring)
navix/grid.py:91:0: C0116: Missing function or method docstring (missing-function-docstring)
navix/grid.py:95:0: C0116: Missing function or method docstring (missing-function-docstring)
navix/grid.py:99:0: C0116: Missing function or method docstring (missing-function-docstring)
navix/grid.py:112:0: C0116: Missing function or method docstring (missing-function-docstring)
navix/grid.py:113:32: C0103: Argument name "n" doesn't conform to snake_case naming style (invalid-name)
navix/grid.py:123:0: C0116: Missing function or method docstring (missing-function-docstring)
navix/grid.py:123:37: C0103: Argument name "n" doesn't conform to snake_case naming style (invalid-name)
navix/grid.py:127:0: C0116: Missing function or method docstring (missing-function-docstring)
navix/grid.py:127:20: C0103: Argument name "a" doesn't conform to snake_case naming style (invalid-name)
navix/grid.py:127:30: C0103: Argument name "b" doesn't conform to snake_case naming style (invalid-name)
navix/grid.py:156:0: C0116: Missing function or method docstring (missing-function-docstring)
navix/grid.py:188:0: C0116: Missing function or method docstring (missing-function-docstring)
navix/grid.py:211:0: C0116: Missing function or method docstring (missing-function-docstring)
navix/grid.py:211:0: W0102: Dangerous default value {} as argument (dangerous-default-value)

Report
======
97 statements analysed.

Statistics by type
------------------

+---------+-------+-----------+-----------+------------+---------+
|type     |number |old number |difference |%documented |%badname |
+=========+=======+===========+===========+============+=========+
|module   |2      |NC         |NC         |0.00        |0.00     |
+---------+-------+-----------+-----------+------------+---------+
|class    |0      |NC         |NC         |0           |0        |
+---------+-------+-----------+-----------+------------+---------+
|method   |0      |NC         |NC         |0           |0        |
+---------+-------+-----------+-----------+------------+---------+
|function |19     |NC         |NC         |31.58       |0.00     |
+---------+-------+-----------+-----------+------------+---------+

249 lines have been analyzed

Raw metrics
-----------

+----------+-------+------+---------+-----------+
|type      |number |%     |previous |difference |
+==========+=======+======+=========+===========+
|code      |131    |52.61 |NC       |NC         |
+----------+-------+------+---------+-----------+
|docstring |10     |4.02  |NC       |NC         |
+----------+-------+------+---------+-----------+
|comment   |41     |16.47 |NC       |NC         |
+----------+-------+------+---------+-----------+
|empty     |67     |26.91 |NC       |NC         |
+----------+-------+------+---------+-----------+

Duplication
-----------

+-------------------------+------+---------+-----------+
|                         |now   |previous |difference |
+=========================+======+=========+===========+
|nb duplicated lines      |0     |NC       |NC         |
+-------------------------+------+---------+-----------+
|percent duplicated lines |0.000 |NC       |NC         |
+-------------------------+------+---------+-----------+

Messages by category
--------------------

+-----------+-------+---------+-----------+
|type       |number |previous |difference |
+===========+=======+=========+===========+
|convention |19     |NC       |NC         |
+-----------+-------+---------+-----------+
|refactor   |0      |NC       |NC         |
+-----------+-------+---------+-----------+
|warning    |2      |NC       |NC         |
+-----------+-------+---------+-----------+
|error      |0      |NC       |NC         |
+-----------+-------+---------+-----------+

Messages
--------

+---------------------------+------------+
|message id                 |occurrences |
+===========================+============+
|missing-function-docstring |13          |
+---------------------------+------------+
|invalid-name               |4           |
+---------------------------+------------+
|missing-module-docstring   |2           |
+---------------------------+------------+
|redefined-outer-name       |1           |
+---------------------------+------------+
|dangerous-default-value    |1           |
+---------------------------+------------+

-----------------------------------
Your code has been rated at 7.84/10