Improve root module discovery error handling

[radeksimko]

This slightly improves logging, where previously we'd log error from plugin cache updating separately and then report 0 errors from loading a module, now all the loading stages are treated the same in terms of error reporting.
The relevant error is however still (intentionally) ignored as watcher invokes these methods:

terraform-ls/internal/watcher/watcher.go

Lines 89 to 94 in 2347f8d

	for _, h := range w.changeHooks {
	err := h(ctx, newTf)
	if err != nil {
	w.logger.Println("change hook error:", err)
	}
	}

Secondly this also improves the message we show when there is no root module found, to be more helpful until #222 is implemented and reflect that the message is related to the directory, rather than file.

[ghost]

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