[Bug][python] exists raises exception in cases when it should return False

[bkmartinjr]

Describe the bug

tiledbsoma.*.exists() is documented as return a False for any URI that does not exist. However, in many cases it will raise an exception instead of returning False.

Simple example: an unknown URI scheme, e.g, tiledbsoma.DataFrame.exists("foo://bar")

The typical pattern in Python (e.g., fsspec) is to swallow all exceptions and return False, e.g.,

In [26]: fsspec.AbstractFileSystem().exists("foo")
Out[26]: False

In [27]: fsspec.AbstractFileSystem().exists("foo://bar")
Out[27]: False

Root cause is the explicit except SOMAError catch in the exists implementation.

Versions (please complete the following information):

tiledbsoma.__version__    1.0.0rc2
tiledb.__version__        0.20.0
core version              2.14.0
python version            3.10.6.final.0