Bare word improvements

[sophiajt]

Description

This does two fixes for bare words:

• It changes completions for paths to wrap a path with backticks if it starts with a number. This helps bare words that start with numbers be separate from unit values
• It allows bare words wrapped with backticks to be the name of a command. Backtick values in command positions are no longer treated as strings

User-Facing Changes

(List of all changes that impact the user experience here. This helps us keep track of breaking changes.)

Tests + Formatting

Don't forget to add tests that cover your changes.

Make sure you've run and fixed any issues with these commands:

• cargo fmt --all -- --check to check standard code formatting (cargo fmt --all applies these changes)
• cargo clippy --workspace -- -D warnings -D clippy::unwrap_used -A clippy::needless_collect to check that you're using the standard code style
• cargo test --workspace to check that all tests pass

After Submitting

If your PR had any user-facing changes, update the documentation after the PR is merged, if necessary. This will help us keep the docs up to date.

[codecov]

Codecov Report

Merging #8066 (88b549e) into main (64b6c02) will decrease coverage by 0.34%.
The diff coverage is 9.09%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #8066      +/-   ##
==========================================
- Coverage   54.90%   54.57%   -0.34%     
==========================================
  Files         605      608       +3     
  Lines       98847    99035     +188     
==========================================
- Hits        54272    54048     -224     
- Misses      44575    44987     +412     

Impacted Files	Coverage Δ
crates/nu-cli/src/completions/file_completions.rs	0.00% <0.00%> (ø)
crates/nu-parser/src/parser.rs	74.39% <100.00%> (-0.17%)	⬇️
crates/nu-engine/src/eval.rs	52.95% <0.00%> (-3.77%)	⬇️
crates/nu-command/src/filters/rename.rs	79.28% <0.00%> (-2.31%)	⬇️
crates/nu-protocol/src/engine/stack.rs	75.83% <0.00%> (-1.03%)	⬇️
crates/nu-test-support/src/fs.rs	23.25% <0.00%> (-0.56%)	⬇️
crates/nu-parser/src/parse_keywords.rs	40.32% <0.00%> (-0.45%)	⬇️
crates/nu-protocol/src/value/mod.rs	47.48% <0.00%> (-0.38%)	⬇️
crates/nu-parser/src/type_check.rs	25.49% <0.00%> (-0.23%)	⬇️
crates/nu-command/src/viewers/table.rs	31.67% <0.00%> (-0.22%)	⬇️
... and 43 more