Create the function declaration schema at construction time

[rlazo]

By creating the schema earlier, any errors when declaring the schema will be caught at the declaration site, which makes debugging much easier.

[github-actions]

Release note changes

No release note changes were detected. If you made changes that should be
present in the next release, ensure you've added an entry in the appropriate
CHANGELOG.md file(s).

[google-oss-bot]

	1 Warning
⚠️	Did you forget to add a changelog entry? (Add the 'no-changelog' label to the PR to silence this warning.)

Generated by 🚫 Danger

[google-oss-bot]

Coverage Report ¹

Affected Products

No changes between base commit (fe9d619) and merge commit (7f05293).

Test Logs

• Base (fe9d619): https://github.com/firebase/firebase-android-sdk/actions/runs/11018020376
• Merge (7f05293): https://github.com/firebase/firebase-android-sdk/actions/runs/11019051331

1. https://storage.googleapis.com/firebase-sdk-metric-reports/HxLvxwFqLR.html

[github-actions]

Unit Test Results

  16 files   -    274    16 suites   - 274   16s ⏱️ - 8m 17s
107 tests  - 1 755  107 ✔️  - 1 738  0 💤  - 17  0 ❌ ±0 
214 runs   - 3 550  214 ✔️  - 3 516  0 💤  - 34  0 ❌ ±0 

Results for commit 5b2494f. ± Comparison against base commit fe9d619.

♻️ This comment has been updated with latest results.

[google-oss-bot]

Size Report ¹

Affected Products

• firebase-vertexai

  Type	Base (fe9d619)	Merge (7f05293)	Diff
  aar	464 kB	464 kB	+3 B (+0.0%)
  apk (release)	9.29 MB	9.29 MB	+60 B (+0.0%)

Test Logs

• Base (fe9d619): https://github.com/firebase/firebase-android-sdk/actions/runs/11018020376
• Merge (7f05293): https://github.com/firebase/firebase-android-sdk/actions/runs/11019051331

1. https://storage.googleapis.com/firebase-sdk-metric-reports/i3DV22sZe9.html