Testing module improvements

[matt2e]

• Is there a way to specify which project toml to use in tests? #1309
• common/configuration should not be used in go-runtime #1370
• ftltest.WithConfig and ftltest.WithSecret should not update project toml #1383
• make sure ftl.Map handles changes in underlying values correctly #1390
• add ftltest.WithProjectFile(...) option #1391
• add WithDatabase(handle) #1392
• ModuleContext should be immutable to avoid threading issues #1398

PRs without issues:

• fix: test context strictly enforces names and types #1360
• feat: module tests can declare config/secrets/DSNs and add verb mocks #1317
• feat: module unit tests can allow calls within module #1373