Update Bazel configuration and dependencies

[mmorel-35]

TODO: Please describe your changes here.

• Bump Bazel version to 7.6.1 in .bazeliskrc
• Add common flag for Bazel module support in .bazelrc
• Include MODULE.bazel file for module definition
• Add WORKSPACE.bzlmod file for module workspace
• Update BUILD file to include necessary headers
• Add MODULE.bazel.lock to .gitignore

TODO: Please read the following on ICU Contributing, and then delete these instructions.

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    • ICU 78 code warnings/version updates: ICU-23054 — Fix compiler warnings. Update versions of code-related dependencies (e.g., dependabot).
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TODO: Fill out the checklist below.

Checklist

• Required: Issue filed: ICU-NNNNN
• Required: The PR title must be prefixed with a JIRA Issue number. Example: "ICU-1234 Fix xyz"
• Required: Each commit message must be prefixed with a JIRA Issue number. Example: "ICU-1234 Fix xyz"
• Issue accepted (done by Technical Committee after discussion)
• Tests included, if applicable
• API docs and/or User Guide docs changed or added, if applicable

[mmorel-35]

I created an account on jira but couldn't create an issue, can someone help on that ?

[jira-pull-request-webhook]

Notice: the branch changed across the force-push!

• MODULE.bazel is different

View Diff Across Force-Push

~ Your Friendly Jira-GitHub PR Checker Bot

[echeran]

Although the PR description matches what the PR is doing, it's still not clear why the PR was created. In other words, what is the desired end goal that this PR solves (partially or wholly)?

Note: ICU only uses the Bazel build for building Unicode data that gets included in the headers of C++ files. Doing so requires building tools that depend circularly on those data header files.