Autocomplete: Fix loading indicator and deletion opt-out (#456)

Two quick fixes for regressions I introduced in #412

- Loading indicator felt flaky so this this PR makes sure we start the
indicator a bit earlier and terminate in any case.
- The opt-out for a deletion case was wrong, causing it to skip the
condition if the last action was a deletion and there was no cache
response. This was not intended to be changed for now. The correct
behavior should still be: If there is a deletion, ONLY continue if twe
have an exact cache response. Otherwise return no completions.

## Test plan

- tested locally,

<!-- Required. See
https://docs.sourcegraph.com/dev/background-information/testing_principles.
-->

vscode/src/completions/index.ts

@@ -154,8 +154,8 @@ export class CodyCompletionItemProvider implements vscode.InlineCompletionItemPr
         tracer?.({ params: { document, position, context } })
 
         const abortController = new AbortController()
+        this.abortOpenCompletions()
         if (token) {
-            this.abortOpenCompletions()
             token.onCancellationRequested(() => abortController.abort())
             this.abortOpenCompletions = () => abortController.abort()
         }
@@ -225,7 +225,7 @@ export class CodyCompletionItemProvider implements vscode.InlineCompletionItemPr
             // render if you insert whitespace but not on the original place when you delete it
             // again
             cachedCompletions = this.config.cache?.get(prefix, false)
-            if (cachedCompletions && !cachedCompletions.isExactPrefix) {
+            if (!cachedCompletions?.isExactPrefix) {
                 return emptyCompletions()
             }
         }
@@ -348,6 +348,15 @@ export class CodyCompletionItemProvider implements vscode.InlineCompletionItemPr
 
         CompletionLogger.start(logId)
 
+        const stopLoading = this.config.statusBar.startLoading('Completions are being generated')
+        this.stopLoading = stopLoading
+        // Overwrite the abort handler to also update the loading state
+        const previousAbort = this.abortOpenCompletions
+        this.abortOpenCompletions = () => {
+            previousAbort()
+            stopLoading()
+        }
+
         const contextResult = await this.config.contextFetcher({
             document,
             prefix,
@@ -365,16 +374,6 @@ export class CodyCompletionItemProvider implements vscode.InlineCompletionItemPr
 
         CompletionLogger.networkRequestStarted(logId, contextResult.logSummary)
 
-        const stopLoading = this.config.statusBar.startLoading('Completions are being generated')
-        this.stopLoading = stopLoading
-
-        // Overwrite the abort handler to also update the loading state
-        const previousAbort = this.abortOpenCompletions
-        this.abortOpenCompletions = () => {
-            previousAbort()
-            stopLoading()
-        }
-
         const completions = await this.requestManager.request(
             document.uri.toString(),
             logId,