Same module cannot appear in multiple disable_error_code overrides

Bug Report

In my pyproject.toml file I have created some overrides to disable specific checks for specific files.

This is because I am adding type checking to an existing legacy repository, I don't have the time to update all the existing legacy code, but don't want to disable the checks entirely - when we write new code I'd like it to be properly type-checked.

When I include the same module in two [[tool.mypy.overrides]] I get a conflict error...

To Reproduce

Add the same module into multiple overrides blocks:

[[tool.mypy.overrides]]
disable_error_code = [
    "attr-defined",
]
module=[
    "foo.bar.baz",
    "my.other.module",
]

[[tool.mypy.overrides]]
disable_error_code = [
    "union-attr",
]
module=[
    "foo.bar.baz",
]

I get the error:
pyproject.toml: toml config file contains [[tool.mypy.overrides]] sections with conflicting values. Module 'foo.bar.baz' has two different values for 'disable_error_code'

Expected Behavior

It should permit a module being in multiple overrides blocks.

The reason this is advantageous is because a given check (e.g. "union-attr") may need a different set of module exceptions to another check.

Actual Behavior

The error prevents this setup from functioning.

Your Environment

• Mypy version used: 1.5.0
• Mypy command-line flags: None
• Mypy configuration options from mypy.ini (and other config files):

[tool.mypy]
python_version = "3.9"
warn_unused_ignores = true
no_implicit_optional = false
no_strict_optional = true
allow_redefinition = true
disable_error_code = [
    "annotation-unchecked",  # Suppress warning notes
    "no-redef", # this one is just annoying
]

exclude = [
    <Some paths>
]

# This ignores mypy for libraries that do not themselves use type annotations.
[[tool.mypy.overrides]]
module = [
    <Some imports>
]
ignore_missing_imports = true

# Selective disable of override checks
[[tool.mypy.overrides]]
disable_error_code = [
    "override",
]
module=[
    <Some modules>
]

# Selective disable of union-attr checks
[[tool.mypy.overrides]]
disable_error_code = [
    "union-attr",
]
module=[
    <Some modules>
]

# Selective disable of assignment checks
[[tool.mypy.overrides]]
disable_error_code = [
    "assignment",
]
module=[
    <Some modules>
]

# Selective disable of call-overload checks
[[tool.mypy.overrides]]
disable_error_code = [
    "call-overload",
]
module=[
    <Some modules>
]

# Selective disable of arg-type checks
[[tool.mypy.overrides]]
disable_error_code = [
    "arg-type",
]
module=[
    <Some modules>
]

# Selective disable of misc checks
[[tool.mypy.overrides]]
disable_error_code = [
    "misc",
]
module=[
    <Some modules>
]

# Selective disable of attr-defined checks
[[tool.mypy.overrides]]
disable_error_code = [
    "attr-defined",
]
module=[
    <Some modules>
]

• Python version used: 3.9.17

Start by reproducing the conflict with the provided pyproject.toml [[tool.mypy.overrides]] configuration and the mypy 1.5.0 example. Trace how multiple override blocks are validated and merged, then verify that the same module can specify separate disable_error_code values without a conflict. Done means the example configuration is accepted while existing conflicting-value validation still behaves correctly.