fix(bazel): Remove monolith imports from Python µgen Bazel rules

[miraleung]

This is needed so that we can remove the monolith from googleapis's switched_rules_by_language. Without this change, py_gapic targets that depend on a proto_library_with_info target will fail to build, because the monolith import clobbers the @rules_gapic//:proto_library_with_info import in googleapis.

We need to temporarily disable the integration tests because the googleapis depndencies (e.g. asset_proto) were themselves dependent on the monolith's rules... but that import must be removed here in order to facilitate removing the monolith from googleapis. These tests will be re-enabled once the googleapis change is done.

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@0dfac03). Click here to learn what that means.
The diff coverage is 100.00%.

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@@            Coverage Diff             @@
##             master      #923   +/-   ##
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  Coverage          ?   100.00%           
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  Files             ?        27           
  Lines             ?      1703           
  Branches          ?       347           
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  Hits              ?      1703           
  Misses            ?         0           
  Partials          ?         0           

Impacted Files	Coverage Δ
gapic/schema/__init__.py	100.00% <ø> (ø)
gapic/generator/generator.py	100.00% <100.00%> (ø)
gapic/samplegen/__init__.py	100.00% <100.00%> (ø)
gapic/samplegen/manifest.py	100.00% <100.00%> (ø)
gapic/samplegen/samplegen.py	100.00% <100.00%> (ø)
gapic/samplegen_utils/__init__.py	100.00% <100.00%> (ø)
gapic/samplegen_utils/types.py	100.00% <100.00%> (ø)
gapic/samplegen_utils/utils.py	100.00% <100.00%> (ø)
gapic/samplegen_utils/yaml.py	100.00% <100.00%> (ø)
gapic/schema/api.py	100.00% <100.00%> (ø)
... and 14 more

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