Completion for module MCR/ACR references is very dependent on the cursor being at particular parts of the string

### top-level
`module a ''`: works as expected
`module a 'b'`: no MCR/ACR completion (expecting 'br/')
`module a 'br'`: no MCR/ACR completion (expecting 'br/')
### alias
`module a 'br/'`: works as expected
`module a 'br/p'`: no MCR/ACR completion (expecting 'br/public:')
`module a 'br/p'`: no MCR/ACR completion (expecting 'br/public:')
### modulename
`module a 'br/public:'`: works as expected
`module a 'br/public:app'`: no completion (expected 'br/public:app/dapr-containerapp:', 'br/public:app/dapr-containerapps-environment:')
`module a 'br/public:app/'`: no completion (expected 'br/public:app/dapr-containerapp:', 'br/public:app/dapr-containerapps-environment:')
### version
`module a 'br/public:app/dapr-containerapp:'`: works as expected
`module a 'br/public:app/dapr-containerapps-environment:1'`: no completion

Examples:

Reproduce the listed module MCR/ACR completion cases in the editor, checking each cursor position from the issue body. Trace the completion entry point and compare behavior for partial aliases, module names, and versions; done means each example offers the expected completion regardless of cursor placement.

Written by the indexing model from the issue text.