Support inferring distribution from .java-version and .tool-versions files

[Copilot]

Description:

Makes the distribution input optional when a version file already names a distribution. Previously only .sdkmanrc (suffix, e.g. java=21.0.5-tem) could infer the distribution; this extends inference to jenv-style .java-version and asdf-style .tool-versions files using a distribution prefix.

# .java-version
temurin-21.0.5

# .tool-versions
java temurin-21.0.5

• Parsing (src/util.ts) — getVersionFromFileContent now captures an optional distribution identifier from .java-version and .tool-versions, in addition to the existing .sdkmanrc suffix handling. Version extraction is unchanged.
• Mapping — New mapJavaVersionFileDistribution validates the identifier against SUPPORTED_DISTRIBUTIONS (src/constants.ts), stripping arch suffixes (temurin64 → temurin). Unsupported/generic prefixes (e.g. openjdk64) are ignored, falling back to the distribution input so existing behavior is preserved.
• Docs — Updated README.md, action.yml, and docs/advanced-usage.md to describe prefix-based inference.
• Tests — Added .java-version/.tool-versions unit cases in __tests__/util.test.ts (including the hyphen-separator edge case) and an e2e job in e2e-versions.yml that installs with the distribution inferred and no distribution input.

Note: when a file specifies a supported distribution, it takes precedence over the distribution input.

Check list:

• Ran npm run check locally (format, lint, build, test) and all checks pass.
• Mark if documentation changes are required.
• Mark if tests were added or updated to cover the changes.

[brunoborges]

@copilot .java-version file format does not accept distribution